0:00:02 > 0:00:06This programme contains scenes which some viewers may find disturbing.
0:00:06 > 0:00:09There are about 600 murders in the UK each year.
0:00:09 > 0:00:11That's around two a day.
0:00:13 > 0:00:17And, globally, about 50 people are murdered every hour.
0:00:21 > 0:00:23Murder appals and repels us.
0:00:23 > 0:00:25But it also fascinates.
0:00:26 > 0:00:28So, what makes people murder?
0:00:28 > 0:00:30I felt like God.
0:00:30 > 0:00:33The power of God over a human being.
0:00:33 > 0:00:36I went into the kitchen and put my bowl of ice cream down.
0:00:36 > 0:00:39I grabbed a knife from the counter,
0:00:39 > 0:00:41and I stabbed Larry and my mom.
0:00:43 > 0:00:45Are some people born to kill?
0:00:45 > 0:00:48Or are they driven to it by circumstance?
0:00:49 > 0:00:52For 50 years, Horizon and the BBC have been following the work
0:00:52 > 0:00:56of scientists, as they struggle to delve into the minds
0:00:56 > 0:01:00of murderers, to try to understand why people kill.
0:01:02 > 0:01:04The hope is that by understanding
0:01:04 > 0:01:06what makes people into murderers,
0:01:06 > 0:01:09we might, one day, be able to prevent it.
0:01:29 > 0:01:32On the 21st December, 1997,
0:01:33 > 0:01:37a chilling murder took place in a quiet suburb in Ohio.
0:01:40 > 0:01:43Dion Sanders had broken into his grandparents house,
0:01:43 > 0:01:44looking for money.
0:01:45 > 0:01:49But they came home early and caught him in the act.
0:01:49 > 0:01:51It ended up in a big argument.
0:01:51 > 0:01:54A bad argument.
0:01:54 > 0:01:57Next thing I know, I'm beating on them.
0:01:57 > 0:01:59I mean, I'm...I'm...
0:01:59 > 0:02:01I remember I was in such a rage...
0:02:01 > 0:02:03..that they couldn't stop me.
0:02:05 > 0:02:06A frying pan came into it.
0:02:09 > 0:02:12To this day, I have no idea whether I grabbed it,
0:02:12 > 0:02:15or if they grabbed it to try to stop me.
0:02:20 > 0:02:22Dion's grandparents had to defend
0:02:22 > 0:02:26themselves against an increasingly frenzied attack.
0:02:27 > 0:02:30I knew grandpa had a shotgun in the house.
0:02:30 > 0:02:32I remember looking through the door,
0:02:35 > 0:02:38and seeing grandma take the gun up off the floor.
0:02:38 > 0:02:41I ended up getting the gun away from her.
0:02:47 > 0:02:49I remember ending up behind her.
0:02:51 > 0:02:53I remember loading the gun.
0:02:56 > 0:02:58And I pointed at her and shot.
0:03:04 > 0:03:07I remember her falling to the ground.
0:03:10 > 0:03:12I remember reloading it.
0:03:12 > 0:03:14I ran into the garage,
0:03:14 > 0:03:17I pointed at my grandpa and fired.
0:03:19 > 0:03:21I don't know where I hit him.
0:03:23 > 0:03:24I know I shot him.
0:03:37 > 0:03:40For most of us, the idea of violently killing
0:03:40 > 0:03:41another human being,
0:03:41 > 0:03:45particularly your grandparents, is so abhorrent, we assume that
0:03:45 > 0:03:49anyone who is capable of it must have something wrong with them.
0:03:49 > 0:03:50But is that right?
0:03:50 > 0:03:53Are murderers really that different to the rest of us?
0:03:58 > 0:03:59In the 1870s,
0:03:59 > 0:04:03science began to take its first faltering steps
0:04:03 > 0:04:05towards answering this question.
0:04:06 > 0:04:10Dr Cesare Lombroso, the father of scientific criminology,
0:04:10 > 0:04:14was studying criminals imprisoned in Turin and Pavia.
0:04:21 > 0:04:24'One November morning in 1871,
0:04:24 > 0:04:28'Lombroso made what he thought was a great scientific discovery,
0:04:28 > 0:04:31'when he studied the skull of the famous Italian thief
0:04:31 > 0:04:34'known as Villela.'
0:04:37 > 0:04:39'I found in the occipital part,
0:04:39 > 0:04:43'exactly on the post where the spine is found in a normal skull,
0:04:43 > 0:04:46'a distinct impression, as an inferior animal's.
0:04:46 > 0:04:48'In particular, rodents.
0:04:48 > 0:04:53'I suddenly saw, lit up as a vast plain under the flaming sky,
0:04:53 > 0:04:55'the nature of the criminal.
0:04:55 > 0:04:58'An atavistic being who reproduces the ferocious
0:04:58 > 0:05:02'instincts of humanity and of the inferior animal.'
0:05:08 > 0:05:11Lombroso believed he had found evidence that a criminal's
0:05:11 > 0:05:14brain is different to that of a noncriminal.
0:05:14 > 0:05:17A step back in evolution.
0:05:17 > 0:05:19He claims that this was clearly displayed in the shape
0:05:19 > 0:05:21of a criminal's face.
0:05:23 > 0:05:26'A criminal's ears are often of a large size,
0:05:26 > 0:05:28'and the nose is frequently upturned,
0:05:28 > 0:05:32'or of a flattened character in thieves.
0:05:32 > 0:05:35'In murderers, it is often aquiline, like the beak of a bird of prey.'
0:05:41 > 0:05:44Lombroso's approach was soon discredited,
0:05:44 > 0:05:47but it was the beginning of a big idea.
0:05:47 > 0:05:49That criminals, and in particular murderers,
0:05:49 > 0:05:52have different brains to the rest of us.
0:05:52 > 0:05:56The studies he conducted back in the 1800s, by today's standards
0:05:56 > 0:05:59might be laughable, but, at the same time, it was a beginning.
0:05:59 > 0:06:01And what Lombroso did was open the door.
0:06:01 > 0:06:04He built a foundation for others to build on.
0:06:08 > 0:06:12But it was almost 100 years before science was able to provide
0:06:12 > 0:06:16the tools to really start exploring the mind of a murderer.
0:06:26 > 0:06:29The first crucial step was research with animals,
0:06:29 > 0:06:32in the 1950s and '60s.
0:06:32 > 0:06:35Scientists wanted to know if there were specific
0:06:35 > 0:06:38parts of the brain responsible for producing aggression.
0:06:40 > 0:06:42In one ground-breaking study,
0:06:42 > 0:06:44cats were implanted with electrodes,
0:06:44 > 0:06:47and these were used to electrically stimulate different
0:06:47 > 0:06:49parts of their brains.
0:06:50 > 0:06:53The animals, after such an operation,
0:06:53 > 0:06:56are perfectly at ease,
0:06:56 > 0:06:58and they suffer no discomfort.
0:06:58 > 0:07:02And we can keep them like this for a long period of time.
0:07:02 > 0:07:05But, when we stimulate, the first thing we see,
0:07:05 > 0:07:08with the smallest amount of current we can use,
0:07:08 > 0:07:10is this alerting behaviour.
0:07:10 > 0:07:12The pupils are dilated, the ears are pricked,
0:07:12 > 0:07:15and the head might be raised a little.
0:07:15 > 0:07:18The heart is working much harder, ready for the muscular exertion
0:07:18 > 0:07:21which we soon see if we stimulate a little bit harder.
0:07:21 > 0:07:23'Then, when the current is switched on,
0:07:23 > 0:07:26'the cat attacks the first object it sees.
0:07:26 > 0:07:28'In this case, a dummy cat.'
0:07:33 > 0:07:37Animal experiments like these provided strong evidence
0:07:37 > 0:07:41that specific parts of the brain are involved in producing violent
0:07:41 > 0:07:43and aggressive emotional reactions.
0:07:44 > 0:07:48The key area is called the amygdala.
0:07:48 > 0:07:52So, might the amygdala play a part in human violence and even murder?
0:07:59 > 0:08:04In 1969, the dramatic case of a patient known only as Julie
0:08:04 > 0:08:08gave scientists a rare opportunity to measure activity directly
0:08:08 > 0:08:13from the amygdala of someone who had come close to committing a murder.
0:08:14 > 0:08:17Julie suffered from epilepsy.
0:08:17 > 0:08:20During her fits, she often experienced fear
0:08:20 > 0:08:22and a sense of panic.
0:08:22 > 0:08:26Then all the strange feeling would come over me.
0:08:26 > 0:08:31Frightening feeling. Strange and stronger than hell.
0:08:32 > 0:08:37One day, while at the cinema, Julie was overcome by a fit
0:08:37 > 0:08:41and during that fit, she stabbed a young girl.
0:08:41 > 0:08:45Luckily, the girl survived, but could Julie's epilepsy have
0:08:45 > 0:08:47been responsible for this violent attack?
0:08:51 > 0:08:56Dr Vernon Mark treated Julie after the incident.
0:08:56 > 0:09:01What we did was to put a special guiding machine on to her skull,
0:09:01 > 0:09:03under general anaesthesia.
0:09:03 > 0:09:08And I inserted a needle inside her temporal lobes,
0:09:08 > 0:09:12very close to the amygdala, and once we did this,
0:09:12 > 0:09:18we then recorded the electrical activity, trying to determine
0:09:18 > 0:09:22what site was firing off when she had her ordinary seizures.
0:09:22 > 0:09:26Using a technique newly developed in animal research,
0:09:26 > 0:09:30the neurologists received signals transmitted by radio
0:09:30 > 0:09:33from electrodes implanted deep in Julie's brain.
0:09:33 > 0:09:38They monitored her brainwaves during normal activity,
0:09:38 > 0:09:41while she was resting,
0:09:41 > 0:09:44and also during her seizures.
0:09:44 > 0:09:47And then, more controversially,
0:09:47 > 0:09:50Vernon Mark's team reversed the signal.
0:09:50 > 0:09:54And so, instead of recording activity, stimulated her brain.
0:09:54 > 0:09:58Some seconds after the stimulation was initiated,
0:09:58 > 0:10:01the patient became unresponsive and she began to stare
0:10:01 > 0:10:06and then she had facial grimacing,
0:10:06 > 0:10:09almost characteristic of a primitive rage response.
0:10:09 > 0:10:11And during this time,
0:10:11 > 0:10:16we noticed that the patient was producing electrical activity
0:10:16 > 0:10:20that looked like a seizure coming from the amygdala
0:10:20 > 0:10:23and quite suddenly,
0:10:23 > 0:10:26after some seconds of grimacing,
0:10:26 > 0:10:31Julie launched herself against the wall in a sudden attack behaviour,
0:10:31 > 0:10:33smashing her fists against the wall.
0:10:39 > 0:10:43Julie's response to stimulation of the amygdala was strikingly
0:10:43 > 0:10:44similar to that of the cat's.
0:10:46 > 0:10:49Her case proved there could be a direct
0:10:49 > 0:10:53relationship between a violent act and activation of the amygdala,
0:10:53 > 0:10:55the emotional centre of the brain.
0:11:01 > 0:11:05Another unusual clinical case, that of Ted Bledsoe, was
0:11:05 > 0:11:07to implicate a totally different
0:11:07 > 0:11:10part of the brain in murderous behaviour.
0:11:10 > 0:11:13Ted Bledsoe was a doctor,
0:11:13 > 0:11:19a model citizen with no history of violent behaviour.
0:11:19 > 0:11:24- 79, 72...- But then, he changed.
0:11:24 > 0:11:26Gradually, over a ten year period,
0:11:28 > 0:11:33he became increasingly violent for no apparent reason.
0:11:35 > 0:11:42I hit the child of some dear friends who, at that time,
0:11:42 > 0:11:45was about five years old.
0:11:45 > 0:11:50He was teasing me and I hurled off and hit him in the face.
0:11:50 > 0:11:52And I attacked my wife.
0:11:52 > 0:11:58I knocked her down, got on top of her and beat her with my closed fists.
0:11:58 > 0:12:02I know that had I a weapon in my hand,
0:12:02 > 0:12:03I probably would have killed her.
0:12:10 > 0:12:15Finally, after losing everything, Ted was sent for a brain scan.
0:12:15 > 0:12:20This revealed a massive tumour in his prefrontal cortex.
0:12:20 > 0:12:24This is the part of the brain that allows us to control
0:12:24 > 0:12:28our reactions to the emotional impulses produced in the amygdala.
0:12:28 > 0:12:30You can see that there is just no brain there.
0:12:30 > 0:12:33There's supposed to be, but there isn't.
0:12:35 > 0:12:39As Ted's case demonstrates, damage to the prefrontal cortex
0:12:39 > 0:12:43makes people less able to control their emotional reactions.
0:12:43 > 0:12:47There's no way that somebody can say with a straight face that this
0:12:47 > 0:12:50fella, the absence of his frontal lobes has not had any
0:12:50 > 0:12:52behavioural effect on him.
0:12:52 > 0:12:54That would be... That's untenable.
0:12:54 > 0:12:57By disrupting his impulse control,
0:12:57 > 0:13:01the tumour almost made Ted a murderer.
0:13:01 > 0:13:06Cases like Ted and Julie's certainly suggest that the prefrontal cortex
0:13:06 > 0:13:11and the emotional centres of the brain are both involved in murder.
0:13:11 > 0:13:15Yet, brain tumours and epilepsy rarely feature in murder trials.
0:13:15 > 0:13:19So, is there other evidence that murders involve these two
0:13:19 > 0:13:21brain areas?
0:13:23 > 0:13:27The invention of functional brain scanning in the 1980s finally
0:13:27 > 0:13:31allowed psychologists to precisely measure the activity
0:13:31 > 0:13:34going on inside the brain of any murderer.
0:13:34 > 0:13:37The first brain scanning study of murderers was carried
0:13:37 > 0:13:42out in California by British neuroscientist Dr Adrian Raine.
0:13:45 > 0:13:49One of the attractions in coming to California is that one can
0:13:49 > 0:13:55obtain large samples of very violent and homicidal individuals.
0:13:57 > 0:14:01Donta Page was one such murderer.
0:14:01 > 0:14:05Aged just 21, he brutally raped and murdered 24-year-old
0:14:05 > 0:14:10Peyton Tuthill when she came home to find him committing a burglary.
0:14:12 > 0:14:15'I was in the back, by the back door, when I heard the front door.'
0:14:17 > 0:14:23At that time, she encountered the murderer,
0:14:23 > 0:14:27and there was quite a physical battle that ensued after that
0:14:27 > 0:14:30with her trying to protect herself and she got away.
0:14:30 > 0:14:32'I chased her.'
0:14:34 > 0:14:36But he didn't stop.
0:14:40 > 0:14:43He proceeded to stab her many, many times.
0:14:48 > 0:14:51What made Donta Page such a violent killer?
0:14:54 > 0:14:59Looking for answers, Dr Raine scanned his brain.
0:15:00 > 0:15:04'This is the scan of a normal, non-violent person's brain.
0:15:04 > 0:15:08'The warm colours, reds and yellows, indicate normal brain function.
0:15:10 > 0:15:14'Donta Page's scan shows that his brain is not functioning properly.
0:15:14 > 0:15:16'The colours are much cooler.'
0:15:16 > 0:15:22What we can see in this lower scan is that Donta Page's prefrontal
0:15:22 > 0:15:26cortex is functioning much more poorly than that of normal
0:15:26 > 0:15:28people who are non-violent.
0:15:30 > 0:15:35Dr Raine and his team scanned 41 murderers and all of them
0:15:35 > 0:15:38showed reduced functioning of the prefrontal cortex,
0:15:38 > 0:15:43the area which controls our response to our emotional impulses.
0:15:43 > 0:15:46He also found that the emotion-producing
0:15:46 > 0:15:48centres of the brain, like the amygdala, which
0:15:48 > 0:15:54generates our aggressive impulses, were overactive in the murderers.
0:15:54 > 0:15:58So, it seems that murderers have brains that make them
0:15:58 > 0:16:00more prone to rage and anger,
0:16:00 > 0:16:05while at the same time, making them less able to control themselves.
0:16:08 > 0:16:10But it's more complicated than that
0:16:10 > 0:16:13because there are different types of murderer.
0:16:13 > 0:16:17The ones in Dr Raine's study were mainly reactive, impulsive,
0:16:17 > 0:16:21hot-blooded. Then, there are the cold-blooded ones,
0:16:21 > 0:16:26who planned everything in meticulous detail and may kill again and again.
0:16:26 > 0:16:30So, what goes on inside the mind of a serial killer?
0:16:39 > 0:16:44David Krueger is a typical serial killer.
0:16:44 > 0:16:46Like 90% of serial killers,
0:16:46 > 0:16:50he displays the psychological characteristics of a psychopath.
0:16:50 > 0:16:55Aged just 17, he brutally murdered three young children.
0:16:55 > 0:16:59'It all began on the 16th of September 1956.
0:16:59 > 0:17:02'A little boy called Wayne Mallette had gone to
0:17:02 > 0:17:05'visit his grandmother in Toronto.
0:17:05 > 0:17:08'He was playing in the front yard,
0:17:08 > 0:17:11'but when his mother went to look for him, he had vanished.
0:17:19 > 0:17:22'Wayne was fascinated by trains.
0:17:22 > 0:17:25'At some point in the late afternoon,
0:17:25 > 0:17:29'he met with David Krueger. Krueger lured him to a secret place,
0:17:29 > 0:17:31'where he said they could wait for trains together.
0:17:39 > 0:17:43'Six-year-old Wayne was led unsuspecting to his death.
0:17:49 > 0:17:52'He was found a few hours later, brutally murdered.
0:17:54 > 0:17:58'Despite a huge manhunt, Krueger escaped detection.
0:17:58 > 0:18:00'Within three weeks,
0:18:00 > 0:18:05'he persuaded nine-year-old Gary Morris to accept a ride on his bike.
0:18:07 > 0:18:11'He led him to an empty waterfront area by Toronto Docks.
0:18:17 > 0:18:20'When Gary was found dead later that night,
0:18:20 > 0:18:23'he had been choked and viciously attacked.'
0:18:24 > 0:18:28It is too bad that the two boys died,
0:18:28 > 0:18:33but I felt like God, with the power of God over a human being.
0:18:33 > 0:18:38In the strangling of children, I found a degree and sensation
0:18:38 > 0:18:43of pleasure and of accomplishment that I didn't feel anywhere else.
0:18:43 > 0:18:46David Krueger went on to kill four-year-old
0:18:46 > 0:18:51Carole Voyce before finally being arrested.
0:18:51 > 0:18:57Now, had I for one instance thought, "This is a human being, this
0:18:57 > 0:19:03"is somebody who is been badly hurt by me," I think I would have stopped.
0:19:03 > 0:19:08The fact that I didn't shows that those feelings were really secondary.
0:19:12 > 0:19:18It's clear that David Krueger had no concern whatsoever for his victims.
0:19:20 > 0:19:23And this is the key hallmark of a psychopath.
0:19:25 > 0:19:29The essential features of psychopathy would include
0:19:29 > 0:19:32a lack of empathy. I don't mean just a general...
0:19:32 > 0:19:35I mean a profound lack of empathy.
0:19:35 > 0:19:38A general callousness towards other people.
0:19:38 > 0:19:41These are people without a conscience.
0:19:41 > 0:19:45I didn't feel any sense of remorse or guilt at the time, I just
0:19:45 > 0:19:47wanted to create a balance.
0:19:47 > 0:19:50Two boys had died, so maybe now a girl should die.
0:19:54 > 0:19:58To try to understand why they have this extreme lack of empathy
0:19:58 > 0:20:03for others, Bob Hare began to explore the brains of psychopaths.
0:20:13 > 0:20:17We actually showed our subjects a series of pictures
0:20:17 > 0:20:21and some of these pictures are neutral and rather innocuous, others
0:20:21 > 0:20:24are horrific, appalling, would make most people extremely upset.
0:20:24 > 0:20:28They were very distressing.
0:20:28 > 0:20:31Hare looked at the psychopaths' emotional brain,
0:20:31 > 0:20:34while they were looking at the images.
0:20:34 > 0:20:36The results were striking.
0:20:38 > 0:20:42'This is a scan of a normal person looking at violent images.
0:20:42 > 0:20:46'The red shows a great deal of activity in the amygdala.
0:20:46 > 0:20:51'By contrast, the psychopath has almost no activity.
0:20:51 > 0:20:54'There was no difference in the way they processed neutral
0:20:54 > 0:20:56'and emotional images.'
0:20:57 > 0:21:01This lack of emotional activity in the amygdala in response to seeing
0:21:01 > 0:21:05others' suffering explains the chilling lack of empathy
0:21:05 > 0:21:07psychopaths have for their victims.
0:21:07 > 0:21:12I remember jumping on the hillside, up and down, with excitement,
0:21:12 > 0:21:16chanting, "Die, die, die," as she was lying there dying.
0:21:20 > 0:21:24Scans also revealed that unlike reactive killers,
0:21:24 > 0:21:27the prefrontal cortex functioned normally in psychopaths.
0:21:27 > 0:21:31They can control their aggressive impulses.
0:21:31 > 0:21:35And it's this combination of self-control with no empathy
0:21:35 > 0:21:38that makes them so dangerous.
0:21:38 > 0:21:42They can carefully plan their attacks without being held
0:21:42 > 0:21:44back by concern for their victims.
0:21:51 > 0:21:55So, scientists had uncovered what is different about the brains
0:21:55 > 0:21:58or reactive killers and psychopaths.
0:21:59 > 0:22:03But there is another type of killer - those who
0:22:03 > 0:22:08suffer from schizophrenia, and only kill while in the grip of madness.
0:22:11 > 0:22:15In the Western world, 5-10% of murders each year are committed
0:22:15 > 0:22:20by someone with schizophrenia, as was the case with Cody Mitten.
0:22:34 > 0:22:39As Cody was growing up, he was a really good little brother -
0:22:39 > 0:22:43loving and energetic and he just...
0:22:43 > 0:22:45He was a great kid.
0:22:47 > 0:22:51I was very proud of Cody. You couldn't ask for a better son.
0:22:51 > 0:22:55Even growing up, he was very lovable, understanding and helpful.
0:22:55 > 0:22:59You need some help? He'd help you.
0:22:59 > 0:23:00He was number one son.
0:23:04 > 0:23:07He had a real close relationship with his mother.
0:23:07 > 0:23:10He loved his mother very true.
0:23:10 > 0:23:14I mean, there was no doubt in nobody's mind that he loved her.
0:23:18 > 0:23:22But in 1997, Cody started acting strangely.
0:23:24 > 0:23:27That night, he just shows up at my place.
0:23:27 > 0:23:31He's holding his stomach, he's saying that he's sick
0:23:31 > 0:23:33and he thinks he's going to die.
0:23:33 > 0:23:36And that he thought he was Jesus Christ.
0:23:38 > 0:23:43Out of the blue, he would come out and say that he was half man
0:23:43 > 0:23:46and half ape.
0:23:46 > 0:23:49He started talking and saying weird...things,
0:23:50 > 0:23:52which was not becoming to Cody.
0:23:54 > 0:23:59I was scared because there was such a drastic change in him.
0:24:03 > 0:24:07Though most schizophrenics are not violent, having schizophrenia
0:24:07 > 0:24:14makes men three times and women 22 times more likely to murder.
0:24:14 > 0:24:18In Cody's case, his illness drove him to kill his mother
0:24:18 > 0:24:20and her boyfriend Larry.
0:24:22 > 0:24:25We're all sitting in the living room and stuff
0:24:25 > 0:24:28and I was hearing voices come out of the TV,
0:24:28 > 0:24:30like they were talking to me, telling me
0:24:30 > 0:24:33that people were trying to kill my family, trying to kill me and stuff.
0:24:33 > 0:24:36None of this made sense to me at all. I was just really fearful.
0:24:36 > 0:24:39Even though my mother was everything to me,
0:24:39 > 0:24:42at this time, I thought she was in cahoots with everybody else,
0:24:42 > 0:24:45trying to kill me, trying to do harm to me and stuff.
0:24:45 > 0:24:52So, I went into the kitchen to put my bowl of ice cream down and...
0:24:52 > 0:24:55In the kitchen sink.
0:24:55 > 0:24:58And I grabbed a knife from the counter and I stabbed Larry
0:24:58 > 0:25:00and my mom and...
0:25:06 > 0:25:08I don't know why... I don't know.
0:25:11 > 0:25:14- OK.- I don't know...- OK.
0:25:16 > 0:25:22I stabbed Larry and my mom... I don't know why. I have no idea why.
0:25:22 > 0:25:24Um...
0:25:29 > 0:25:32To try and understand how schizophrenia could make
0:25:32 > 0:25:34someone more likely to kill,
0:25:34 > 0:25:38scientists scanned the brains of schizophrenics.
0:25:38 > 0:25:41The scans revealed that the emotional centres
0:25:41 > 0:25:46of their brains did not respond normally to the emotions of others.
0:25:46 > 0:25:51And their prefrontal cortex did not function properly either.
0:25:51 > 0:25:55Schizophrenic murderers seem to combine the lack of empathy of a
0:25:55 > 0:26:00psychopath with the lack of impulse control of a reactive killer.
0:26:00 > 0:26:03The use of brain scans has allowed us
0:26:03 > 0:26:07to identify two areas of the brain. One that produces emotion
0:26:07 > 0:26:10and one that controls our response to emotions,
0:26:10 > 0:26:14which appear to malfunction in the brains of murderers.
0:26:14 > 0:26:17Alongside this, scientists have also studied the biochemistry,
0:26:17 > 0:26:20which seems to underline these malfunctions.
0:26:23 > 0:26:27They wanted to see if there were any chemical imbalances affecting
0:26:27 > 0:26:29the brains of murderers.
0:26:29 > 0:26:34The first and most obvious target was the male hormone testosterone.
0:26:34 > 0:26:38Because perhaps the most striking about murder is
0:26:38 > 0:26:40that 90% of murderers are men.
0:26:43 > 0:26:47So, might testosterone play a part in creating a killer brain?
0:26:48 > 0:26:53An important clue came from a notorious serial
0:26:53 > 0:26:55killer in Connecticut in the 1980s.
0:26:56 > 0:26:58'Michael Ross says a powerful
0:26:58 > 0:27:02'and irresistible urge to hurt women could come over him at any time
0:27:02 > 0:27:06'and at any place, for no apparent reason and with no warning.'
0:27:10 > 0:27:15'You cannot imagine what it is like
0:27:15 > 0:27:18'to be excited and to be stimulated
0:27:18 > 0:27:20'by thoughts of killing somebody,
0:27:20 > 0:27:23'by raping and killing and degrading.'
0:27:23 > 0:27:27They are extremely stimulating and satisfying in the short term,
0:27:27 > 0:27:32but they're disgusting as hell and I wish that I didn't have them.
0:27:36 > 0:27:40Michael Ross was diagnosed as having abnormally high
0:27:40 > 0:27:43levels of testosterone.
0:27:43 > 0:27:46So, could there be a link between high testosterone
0:27:46 > 0:27:48and violent crimes?
0:27:48 > 0:27:51This question led Professor James Dabbs to collect
0:27:51 > 0:27:56and test saliva samples from hundreds of prisoners.
0:27:56 > 0:27:59We examined prison inmates and looked at the testosterone level
0:27:59 > 0:28:02and related it back to the crimes they had committed and found that the
0:28:02 > 0:28:06higher testosterone inmates had more often committed violent crimes.
0:28:07 > 0:28:11Of course, not everyone with high testosterone is a killer.
0:28:11 > 0:28:14But high levels of it do make violence more likely.
0:28:14 > 0:28:19And the very latest research has found that giving normal men
0:28:19 > 0:28:24extra testosterone increases the reactivity of their amygdala,
0:28:24 > 0:28:28the emotional centre of the brain which scanning had revealed was
0:28:28 > 0:28:30overactive in many murderers.
0:28:31 > 0:28:36This could explain the link between testosterone and violence.
0:28:40 > 0:28:44Meanwhile, scientists were also investigating another chemical
0:28:44 > 0:28:48that they suspected might be implicated in murder - serotonin.
0:28:51 > 0:28:55It's a neurotransmitter that is important for the functioning of
0:28:55 > 0:28:58the prefrontal cortex, the area of the brain that is
0:28:58 > 0:29:03crucial for regulating our emotional impulses.
0:29:03 > 0:29:06The first clues came from studies with monkeys.
0:29:09 > 0:29:13If you look at monkeys who have low serotonin, then what you
0:29:13 > 0:29:17see are monkeys that have what we call an antisocial personality.
0:29:17 > 0:29:20These are monkeys that nobody wants to associate with
0:29:20 > 0:29:23because they're likely to beat up other monkeys,
0:29:23 > 0:29:27or likely to do the kinds of things that really are an unpleasant
0:29:27 > 0:29:30kind of relationship to have.
0:29:30 > 0:29:33So, scientists wondered if the same might be true of humans.
0:29:38 > 0:29:41'Striking evidence came from a study of Marines who'd
0:29:41 > 0:29:46'served in Vietnam, but whose behaviour was causing concern.
0:29:46 > 0:29:49'The clue to their overtly aggressive behaviour was
0:29:49 > 0:29:53'discovered for the first time by Dr Fred Goodwin
0:29:53 > 0:29:56'when he studied hundreds of Marines whose violent behaviour went
0:29:56 > 0:29:58'well beyond the call of duty.'
0:30:01 > 0:30:06We dug into their charts and found that there was lots of histories
0:30:06 > 0:30:09of violent and aggressive behaviour
0:30:09 > 0:30:10in many of these individuals.
0:30:12 > 0:30:15He found the violent men shared a key characteristic -
0:30:15 > 0:30:20unusually low levels of the brain chemical serotonin.
0:30:20 > 0:30:23It's a modulator, a dampener, and it is a brake.
0:30:23 > 0:30:27It's a brake and so low serotonin seems to take the brakes off.
0:30:27 > 0:30:32His discovery that low serotonin can increase violent behaviour
0:30:32 > 0:30:34was a scientific turning point.
0:30:34 > 0:30:38Could a lack of serotonin allow some men to kill?
0:30:41 > 0:30:44The case of Deion Sanders, who had brutally murdered
0:30:44 > 0:30:47his elderly the grandparents, provided further evidence
0:30:47 > 0:30:50that serotonin could play a part in murder.
0:30:50 > 0:30:52Sanders.
0:30:55 > 0:31:00In prison, Dr Paul Ross measured Deion's serotonin levels.
0:31:00 > 0:31:02A very abnormally low level of serotonin
0:31:02 > 0:31:08has been linked to many impulsive disorders including aggression,
0:31:08 > 0:31:10unopposed aggression, or rage.
0:31:10 > 0:31:13In the case of Deion Sanders,
0:31:13 > 0:31:17his serotonin level was very abnormally low,
0:31:17 > 0:31:19extremely abnormally low.
0:31:19 > 0:31:23Extremely low levels of serotonin put Deion amongst an unknown number
0:31:23 > 0:31:26of men with a heightened risk of losing their temper,
0:31:26 > 0:31:32capable of sudden and unrestrained violence, capable of murder.
0:31:39 > 0:31:41Over the last 50 years, we've discovered
0:31:41 > 0:31:45a number of biological differences between the brains of murderers
0:31:45 > 0:31:49and the rest of us, but what causes of those differences?
0:31:49 > 0:31:53Is there a genetic component or is it entirely environmental?
0:31:53 > 0:31:55Are murderers born or are they made?
0:31:59 > 0:32:02Initially, scientists focused on the role of upbringing.
0:32:03 > 0:32:08Experiments with monkeys in the late 1950s and early 1960s
0:32:08 > 0:32:10revealed the importance of motherly love
0:32:10 > 0:32:14for the normal psychological development of baby monkeys.
0:32:14 > 0:32:17In controversial experiments,
0:32:17 > 0:32:21Harry Harlow put baby monkeys in isolation for up to a year.
0:32:22 > 0:32:25All the monkeys came out severely disturbed.
0:32:26 > 0:32:28Lack of normal parental care
0:32:28 > 0:32:31had clearly affected their emotional development.
0:32:34 > 0:32:37And it looked like the same was true of humans.
0:32:37 > 0:32:40Certainly it had been known for some time that murderers
0:32:40 > 0:32:44often had violent and disrupted childhoods.
0:32:46 > 0:32:50Steve Parkus is a classic case of what a terrible childhood
0:32:50 > 0:32:52can do to someone.
0:32:52 > 0:32:54Steve and his brother were abused
0:32:54 > 0:32:57and neglected by their alcoholic parents.
0:33:00 > 0:33:02She was harder on Steve than she was on me,
0:33:02 > 0:33:05cos I was the youngest, probably.
0:33:06 > 0:33:08I always hid behind him
0:33:08 > 0:33:10cos he was bigger than I was, right?
0:33:10 > 0:33:13She started swinging, I just ducked behind him, right?
0:33:14 > 0:33:17In lieu of a baby-sitter, when Linda went out drinking,
0:33:17 > 0:33:21she would just lock the kids in the bathroom, lock the door.
0:33:21 > 0:33:25One time, Steve and Chester sneaked out, out the bathroom window,
0:33:25 > 0:33:28and the police found them and brought them home
0:33:28 > 0:33:34and after they left, she heated up a knife over the stove
0:33:34 > 0:33:36and started burning them
0:33:36 > 0:33:39on bare buttocks with the hot blade of the knife and that was the point
0:33:39 > 0:33:43at which the juvenile authorities became involved in the case.
0:33:46 > 0:33:51The two boys were taken in by their uncle Taylor and aunt Bernice.
0:33:51 > 0:33:55Unfortunately for Steve, it was like out of the frying pan
0:33:55 > 0:33:56and into the fire.
0:33:56 > 0:33:59He was taken away from a schizophrenic mother
0:33:59 > 0:34:05and put in the home where he was raised by a sadistic paedophile.
0:34:05 > 0:34:09Steve Parkus is a very good example of a combination
0:34:09 > 0:34:14of some of the most horrendous abuse that you can possibly imagine,
0:34:14 > 0:34:17sexual and physical, leading to
0:34:17 > 0:34:20a completely unsocialised individual.
0:34:20 > 0:34:24He was a person who was raised absolutely and totally
0:34:24 > 0:34:28without any love, without any affection, without any caring.
0:34:29 > 0:34:36He was used as a thing from the time that he was born until today.
0:34:38 > 0:34:42Aged 17, Steve Parkus ended up in prison.
0:34:43 > 0:34:47The first day that he got to prison, the guards stripped him naked
0:34:47 > 0:34:51and marched him up and down the cell block and auctioned him
0:34:51 > 0:34:52off to the highest bidder.
0:34:54 > 0:34:58He was sold as a sex slave for 60.
0:35:01 > 0:35:03CLOTH TEARS
0:35:03 > 0:35:06In November 1985, while still in prison,
0:35:06 > 0:35:10Steve murdered Mark Steffenhagen, his only friend.
0:35:10 > 0:35:12I put his hands...
0:35:12 > 0:35:13tied his hands and tied his feet...
0:35:15 > 0:35:17..and I laid him over on his back
0:35:17 > 0:35:21and I told him what I was going to do and why.
0:35:21 > 0:35:24And I just started choking him, you know.
0:35:24 > 0:35:26I had my hand around his throat.
0:35:35 > 0:35:38It seemed obvious that a violent, unloving childhood
0:35:38 > 0:35:44played a crucial part in creating a killer, the question was how?
0:35:47 > 0:35:52In 1961, a groundbreaking experiment revealed the effect
0:35:52 > 0:35:55that exposure to violence could have on young children.
0:35:58 > 0:36:02This four-year-old given a Bobo doll to play with for the first time
0:36:02 > 0:36:03shows no tendency to attack it.
0:36:07 > 0:36:11The idea doesn't seem to occur to him and he didn't do so even though
0:36:11 > 0:36:15he was allowed to play with the doll for a considerable period.
0:36:16 > 0:36:17In the experiments,
0:36:17 > 0:36:21the children were allowed to watch an adult attack the doll violently.
0:36:22 > 0:36:26This particular four-year-old was not only generally unaggressive,
0:36:26 > 0:36:29but he hadn't previously learnt to punch.
0:36:42 > 0:36:44But when given a second chance to play with the doll,
0:36:44 > 0:36:47he not only attacked it eagerly and without prompting,
0:36:47 > 0:36:49but copied with surprising accuracy
0:36:49 > 0:36:52the techniques of attack he'd just witnessed.
0:36:52 > 0:36:53This behaviour parallels...
0:36:53 > 0:36:56This may seem obvious to us now,
0:36:56 > 0:36:59but at the time it was a revolutionary finding.
0:36:59 > 0:37:03Witnessing violence made children behave more violently.
0:37:07 > 0:37:12But it's not just a case of children copying adult behaviour.
0:37:12 > 0:37:15We now know that childhood experiences actually affect
0:37:15 > 0:37:19the development of the brain areas involved in controlling aggression.
0:37:21 > 0:37:24Professor Peter Smith is an expert on child psychology.
0:37:24 > 0:37:29He's studying the development of early aggressive behaviour.
0:37:29 > 0:37:32- They know that they each want the scooter...- Yeah.
0:37:32 > 0:37:35..but they're not able to really inhibit those impulses yet.
0:37:35 > 0:37:37That's because of a lack of brain development,
0:37:37 > 0:37:38compared to older children.
0:37:40 > 0:37:44Until the age of three, our impulses run riot.
0:37:46 > 0:37:51There's no stopping the urges which come from the emotional centre,
0:37:51 > 0:37:55but then we start to develop the part of the brain
0:37:55 > 0:38:00that allows us to the control our aggression, the prefrontal cortex.
0:38:03 > 0:38:05Yet, crucially,
0:38:05 > 0:38:10how well this control mechanism works depends on our experiences.
0:38:10 > 0:38:14- What do we do at the nursery? - We share.
0:38:15 > 0:38:19Leon, Kelvin, when the sand timer finishes -
0:38:19 > 0:38:22tell me when it's finished and we can take turns on the bikes, yeah?
0:38:22 > 0:38:24Incredibly, being taught to share
0:38:24 > 0:38:28and take turns actually changes the physical structure of the brain.
0:38:31 > 0:38:34It strengthens the connections between the emotional centre
0:38:34 > 0:38:36and the prefrontal cortex.
0:38:38 > 0:38:41This is what makes us less aggressive.
0:38:43 > 0:38:45It's actually children as young as two
0:38:45 > 0:38:48who are the most frequently aggressive, physically aggressive,
0:38:48 > 0:38:52and they're gradually learning not to be aggressive
0:38:52 > 0:38:54in that way through a socialisation process.
0:38:57 > 0:39:02So childhood experiences actually shape the very parts of the brain
0:39:02 > 0:39:06that scanning had revealed don't function properly in murderers.
0:39:06 > 0:39:10If someone grows up experiencing only violence,
0:39:10 > 0:39:13these brain areas are unlikely to develop normally
0:39:13 > 0:39:17and it is more likely that they too will become violent.
0:39:18 > 0:39:20POLICE RADIO CHATTER
0:39:20 > 0:39:25As well as disrupting the normal wiring up of the brain,
0:39:25 > 0:39:27studies in the 1990s suggested
0:39:27 > 0:39:30that childhood abuse might also be creating killers
0:39:30 > 0:39:34by actually causing physical damage to the brain.
0:39:34 > 0:39:37A lot of these kids have been just thrown downstairs
0:39:37 > 0:39:43and battered against walls, punched, hit, and so the brain itself
0:39:43 > 0:39:45is damaged.
0:39:45 > 0:39:46Let's get a path for the...
0:39:46 > 0:39:49The prefrontal cortex is especially vulnerable.
0:39:49 > 0:39:51If you're an infant and your parent vigorously
0:39:51 > 0:39:55shakes you and your head rocks backwards and forwards,
0:39:55 > 0:40:00the brain inside the skull - if this is the skull and this is the brain -
0:40:00 > 0:40:04it will bang on the bony part of the skull
0:40:04 > 0:40:07and this frontal part of the brain here will get damage
0:40:07 > 0:40:11as it's rocked backwards and forwards inside the skull.
0:40:14 > 0:40:19Donta Page who had brutally murdered Peyton Tuthill in 1999
0:40:19 > 0:40:21is a textbook example.
0:40:21 > 0:40:24As a baby, he was frequently shaken by his mother
0:40:24 > 0:40:28and as he got older, the abuse got worse.
0:40:28 > 0:40:30What are you doing? Come here!
0:40:30 > 0:40:33His mother began to use objects to hit him with,
0:40:33 > 0:40:39including, um, electrical extension cords, shoes, whatever was handy.
0:40:39 > 0:40:42These were not once-a-year beatings,
0:40:42 > 0:40:47they were beatings that occurred almost...daily.
0:40:52 > 0:40:55This physical abuse could help explain
0:40:55 > 0:40:58the malfunctioning of Donta's prefrontal cortex.
0:40:59 > 0:41:02I would tend to be persuaded by the notion
0:41:02 > 0:41:06that the early physical abuse, amongst other things...
0:41:07 > 0:41:11..could likely have led to the brain damage which could likely
0:41:11 > 0:41:15have led to him committing this violent act.
0:41:18 > 0:41:21As the evidence mounted, it seemed clear that killers
0:41:21 > 0:41:25were largely being created by their violent upbringing.
0:41:32 > 0:41:35But only a small proportion of those who have terrible childhoods
0:41:35 > 0:41:38grow up to become murderers.
0:41:38 > 0:41:41Now, studies with twins and adopted children had already
0:41:41 > 0:41:45suggested there is a hereditary component to violence.
0:41:45 > 0:41:49Could it be that there are genes that predispose us to murder?
0:41:53 > 0:41:58The breakthrough came in 1993 with a family in Holland
0:41:58 > 0:42:00where all the men had a history of violence.
0:42:01 > 0:42:0415 years of painstaking research revealed
0:42:04 > 0:42:06that they all lacked the same gene.
0:42:09 > 0:42:12There was one gene that was missing and...
0:42:12 > 0:42:15in the men and all these men were violent...
0:42:17 > 0:42:19..so that kind of supported
0:42:19 > 0:42:21the idea that one gene really controlled a behaviour.
0:42:26 > 0:42:30This gene produces an enzyme called MAOA.
0:42:31 > 0:42:34It regulates the levels of neurotransmitters
0:42:34 > 0:42:37involved in impulse control.
0:42:37 > 0:42:40It turns out that if you lack the MAOA gene
0:42:40 > 0:42:44or have what is known as the "low activity variant",
0:42:44 > 0:42:47you are predisposed to violence.
0:42:47 > 0:42:51This variant became known as the warrior gene.
0:42:54 > 0:42:56And soon after, a gene was discovered
0:42:56 > 0:42:59that controls the levels of serotonin.
0:42:59 > 0:43:04This was the neurotransmitter linked to violent behaviour in monkeys,
0:43:04 > 0:43:08marines and criminals, like Deion Sanders,
0:43:08 > 0:43:10but is having the warrior gene
0:43:10 > 0:43:15or the gene for low serotonin enough to make you a killer?
0:43:17 > 0:43:18For Professor Jim Fallon,
0:43:18 > 0:43:22this question was about to become deeply personal.
0:43:22 > 0:43:26Jim had been researching the brain abnormalities of murderers
0:43:26 > 0:43:31for 11 years, when, one day, a casual conversation with his mother
0:43:31 > 0:43:33revealed a history of murder in his own family.
0:43:35 > 0:43:39As we were discussing this, and different brains,
0:43:39 > 0:43:42I said to him, "You should look into your own history."
0:43:42 > 0:43:45I mean, it was really pretty startling,
0:43:45 > 0:43:48but, you know, I knew it was true because she doesn't make things up.
0:43:48 > 0:43:51Yeah, there were quite a few murderers in that family.
0:43:53 > 0:43:57At least 16 murderers in the one line.
0:44:00 > 0:44:03Hearing this, Jim took the bold decision to run a check
0:44:03 > 0:44:05on the entire family
0:44:05 > 0:44:09for the genes linked to violent psychopathic behaviour.
0:44:11 > 0:44:13Back came the results.
0:44:13 > 0:44:16Everybody had a mix of things in our family.
0:44:16 > 0:44:21It looked like an average sort of mix of these different genes
0:44:21 > 0:44:24that have to do with aggression and all sorts of behaviours,
0:44:24 > 0:44:27except now and again there was this one
0:44:27 > 0:44:29that showed all of these high-risk genes
0:44:29 > 0:44:30and it was mine.
0:44:32 > 0:44:36People with far less dangerous genetics become killers
0:44:36 > 0:44:38and are psychopaths than what I had, you know.
0:44:38 > 0:44:40I had, like, almost all of them.
0:44:40 > 0:44:41It was right up...
0:44:41 > 0:44:46But the reaction from his family was to unsettle him even further.
0:44:48 > 0:44:50'I knew there was always something off.'
0:44:50 > 0:44:53It makes more sense now that
0:44:53 > 0:44:55it's clear that
0:44:55 > 0:44:58he does have the brain and genetics of a psychopath.
0:44:58 > 0:45:01It all falls into place, as it were.
0:45:02 > 0:45:04Those are...
0:45:04 > 0:45:06'I have characteristics or traits,
0:45:06 > 0:45:10'some of which are, you know, that a psychopath...yeah.'
0:45:10 > 0:45:13I could blow off an aunt's funeral if I thought there was a party
0:45:13 > 0:45:19that day - I would just take off and that's not right.
0:45:19 > 0:45:22The thing is I know that now but I still don't care
0:45:22 > 0:45:27and so I know something's wrong, but I still don't care.
0:45:29 > 0:45:30And, er, you know...
0:45:30 > 0:45:32I don't know how else to put that.
0:45:32 > 0:45:35It's just you are in a position where, "Oh, that's not right
0:45:35 > 0:45:38"and I don't give a shit," and that's the truth.
0:45:39 > 0:45:43But Jim isn't a murderer, he's a respected professor.
0:45:43 > 0:45:48It turns out that about 30% of men have the warrior gene
0:45:48 > 0:45:51and 16% have the low serotonin gene
0:45:51 > 0:45:54and clearly most of them are not killers.
0:45:56 > 0:45:59So why isn't everyone with killer genes a murderer?
0:46:01 > 0:46:04The answer is that whether the genes are triggered or not
0:46:04 > 0:46:07will depend on what happens in your childhood.
0:46:09 > 0:46:11'If you have the so-called high risk form of the gene'
0:46:11 > 0:46:14and you're abused early on in life,
0:46:14 > 0:46:17'your chances of spending a life of crime are much higher.
0:46:17 > 0:46:20'If you have the gene, the high risk gene,
0:46:20 > 0:46:23'but you weren't abused then there really wasn't much risk,'
0:46:23 > 0:46:26so just the gene by itself, the variant,
0:46:26 > 0:46:28doesn't really dramatically affect behaviour,
0:46:28 > 0:46:31but under certain environmental conditions, a big difference,
0:46:31 > 0:46:34and that was a very profound finding.
0:46:36 > 0:46:40So what was it about Jim's environment that cancelled out
0:46:40 > 0:46:42his unlucky genes?
0:46:45 > 0:46:48It turns out that I had an unbelievably wonderful childhood.
0:46:51 > 0:46:54I'd go back and look at old movies and old pictures
0:46:54 > 0:46:57and I'm smiling and I'm as happy as a lark
0:46:57 > 0:47:00and you can see it all the way through my life.
0:47:00 > 0:47:03You know, there's a good chance that that offset
0:47:03 > 0:47:05all these genetic factors,
0:47:05 > 0:47:06the brain development and everything
0:47:06 > 0:47:09and it washed that away.
0:47:15 > 0:47:18So it seems that a genetic tendency towards violence
0:47:18 > 0:47:23together with an abusive childhood are a killer combination.
0:47:23 > 0:47:26Murderers are both born and made.
0:47:28 > 0:47:31We now have a far more sophisticated understanding
0:47:31 > 0:47:34of the complex interactions between the social
0:47:34 > 0:47:38and the biological factors that predispose people to murder.
0:47:38 > 0:47:41But what can we do with that knowledge?
0:47:41 > 0:47:45Can we use it to reduce the risk that murderers will reoffend
0:47:45 > 0:47:48or perhaps even prevent them from killing in the first place?
0:47:53 > 0:47:58As far back as the 1950s, we had the ability to use drugs to treat
0:47:58 > 0:48:03some types of potential murderer and reduce the chances of them killing.
0:48:03 > 0:48:07Schizophrenia, in particular, can be successfully treated
0:48:07 > 0:48:09with anti-psychotic medication.
0:48:09 > 0:48:14Cody Mitten had killed his mother while suffering from delusions
0:48:14 > 0:48:17and he was sentenced to life in prison.
0:48:17 > 0:48:19Cody was obviously psychotic because when you went back
0:48:19 > 0:48:22and looked back at the past, two weeks prior to the incident,
0:48:22 > 0:48:23he started to have
0:48:23 > 0:48:25definite psychotic symptoms,
0:48:25 > 0:48:27believing that...
0:48:27 > 0:48:29auditory and visual hallucinations
0:48:29 > 0:48:31along with delusions.
0:48:31 > 0:48:34He believed that voices were coming out of the TV telling him
0:48:34 > 0:48:39to hurt and he believed that others were trying to hurt him.
0:48:39 > 0:48:40While in prison,
0:48:40 > 0:48:43he has been receiving treatment for his schizophrenia
0:48:43 > 0:48:46and as his symptoms have receded,
0:48:46 > 0:48:49the enormity of what he did has sunk in.
0:48:50 > 0:48:51Oh, man, erm...
0:48:54 > 0:48:56HE SOBS
0:48:59 > 0:49:04Oh, I just wish everything was the way it used to be, but it's not, no.
0:49:12 > 0:49:15While his illness is being kept at bay,
0:49:15 > 0:49:17Cody is unlikely to kill again.
0:49:17 > 0:49:20But perhaps his mother's murder could have been avoided
0:49:20 > 0:49:22in the first place.
0:49:22 > 0:49:27I could see it in his eyes, I felt like Cody needed to go to the doctor
0:49:27 > 0:49:29and we needed to take him today.
0:49:31 > 0:49:33Cody's mother took him to the hospital,
0:49:33 > 0:49:35but tragically they sent him home.
0:49:36 > 0:49:42They said everything was normal and I said, "That can't be."
0:49:45 > 0:49:48That night, he killed his mother and her boyfriend Larry.
0:49:50 > 0:49:53Had the doctors detected his schizophrenia and kept him
0:49:53 > 0:49:57in hospital for treatment, they might still be alive today.
0:50:06 > 0:50:10The discovery that brain chemistry was involved in certain murders has
0:50:10 > 0:50:15also led to the development of drugs to treat these chemical imbalances.
0:50:16 > 0:50:19How do you admit that you
0:50:19 > 0:50:22are sexually stimulated by killing someone?
0:50:24 > 0:50:28In particular, drug treatment appears to be effective
0:50:28 > 0:50:31when testosterone is implicated in the crime.
0:50:32 > 0:50:36It's, er, it was like a monster inside me.
0:50:41 > 0:50:43It's so tempting
0:50:43 > 0:50:45just to give into it.
0:50:48 > 0:50:51Michael Ross had abnormally high levels of testosterone
0:50:51 > 0:50:55when he killed eight women in the early 1980s.
0:50:57 > 0:51:01In America, male offenders like Michael are given drugs
0:51:01 > 0:51:04to lower their testosterone levels.
0:51:04 > 0:51:07It's known as chemical castration.
0:51:08 > 0:51:13Michael's testosterone levels fell to 5% of that of most men.
0:51:13 > 0:51:15Writing for a scientific journal,
0:51:15 > 0:51:18he described the effect of the treatment.
0:51:21 > 0:51:25"My obsessive thoughts and urges and fantasies began to diminish.
0:51:26 > 0:51:28"The problem is still there.
0:51:28 > 0:51:32"It's easier to deal with because it isn't always in the foreground,
0:51:32 > 0:51:34"intruding on my everyday life.
0:51:36 > 0:51:38"The monster within is still present
0:51:38 > 0:51:42"but the medication has rendered him impotent.
0:51:42 > 0:51:45"Had I begun receiving just a 1cc injection
0:51:45 > 0:51:51"once a month 15 years ago, eight women would be alive today."
0:51:56 > 0:52:00Studies of violent sex offenders have shown that chemical castration
0:52:00 > 0:52:03cuts reoffending rates to below 5%.
0:52:05 > 0:52:07As well as pharmaceutical interventions,
0:52:07 > 0:52:10scientists also use psychological therapies
0:52:10 > 0:52:13to try and rehabilitate murderers.
0:52:13 > 0:52:17Now, it certainly reduces violent behaviour in many offenders,
0:52:17 > 0:52:21but psychopaths provide a cautionary tale.
0:52:23 > 0:52:27In the 1970s, a group of psychologists in Canada
0:52:27 > 0:52:30were using therapy to treat psychopaths.
0:52:31 > 0:52:35When I arrived at this hospital in 1975,
0:52:35 > 0:52:39the pride of the hospital at that time was this programme
0:52:39 > 0:52:44for psychopaths that was run on four wards of Oakridge.
0:52:44 > 0:52:48And it was considered by everyone at the time to be
0:52:48 > 0:52:50an excellent, excellent programme
0:52:50 > 0:52:53that would be especially beneficial for psychopaths.
0:52:55 > 0:52:58David Krueger was one of the psychopaths on the programme.
0:53:05 > 0:53:08Krueger himself was deemed greatly improved.
0:53:10 > 0:53:13After over 30 years in a maximum security mental hospital,
0:53:13 > 0:53:17he was sent away to a less secure institution at Brockville.
0:53:20 > 0:53:24Marnie Rice and her colleagues followed up treated patients
0:53:24 > 0:53:26to check on the treatment programme's success...
0:53:28 > 0:53:30..but when she compared re-offence rates
0:53:30 > 0:53:32of psychopaths who had been treated
0:53:32 > 0:53:35with psychopaths from prison who had received no treatment at all,
0:53:35 > 0:53:38there was a surprise.
0:53:41 > 0:53:45When we looked at the results and what we saw was
0:53:45 > 0:53:49the programme actually made the psychopaths worse,
0:53:49 > 0:53:50we were astounded.
0:53:50 > 0:53:53I mean, I looked at these data
0:53:53 > 0:53:56and I thought, "There's got to be a mistake here."
0:53:56 > 0:54:00You know, we went back and we checked and checked and checked
0:54:00 > 0:54:03and sure enough, the effect was real.
0:54:03 > 0:54:05It was absolutely the case
0:54:05 > 0:54:08that the programme made the psychopaths worse.
0:54:10 > 0:54:13Many psychopaths have described the therapy programmes
0:54:13 > 0:54:16as finishing schools where they honed their skills.
0:54:16 > 0:54:19I did learn how to manipulate better...
0:54:21 > 0:54:22..um...
0:54:23 > 0:54:26..I did learn how to get control
0:54:26 > 0:54:32of expressing my feelings inappropriately...better...
0:54:33 > 0:54:40..and keep the more outrageous feelings under wraps...better.
0:54:43 > 0:54:45On his first day pass in 35 years,
0:54:45 > 0:54:49David Krueger brutally murdered a fellow inmate.
0:55:00 > 0:55:02For the time being, it seems
0:55:02 > 0:55:05we cannot treat the psychopaths' underlying lack of empathy.
0:55:12 > 0:55:15Scientists are now focusing on using therapy to try
0:55:15 > 0:55:18and prevent murderers being created in the first place.
0:55:19 > 0:55:23They know enough about the causes of murderous behaviour to spot
0:55:23 > 0:55:27early warning signs, and attempt to intervene before it's too late.
0:55:29 > 0:55:31The hope is that therapy will undo
0:55:31 > 0:55:34some of the psychological damage being caused
0:55:34 > 0:55:38by an abusive childhood and prevent children from turning into killers.
0:55:43 > 0:55:46Children, like Justin and his brother Cody,
0:55:46 > 0:55:49who spent their first few years in a violent home.
0:55:50 > 0:55:53When Justin was only two years old, his mother was murdered.
0:55:53 > 0:55:57There was a verbal argument that started between the boyfriend
0:55:57 > 0:56:03and the mother and it led to physical confrontation when they were shoving
0:56:03 > 0:56:06and pushing at each other and then the boyfriend got enraged
0:56:06 > 0:56:09and started to beat her and she kicked at him
0:56:09 > 0:56:13and he picked up a knife and apparently stabbed her in the chest.
0:56:13 > 0:56:15Be careful, Cody.
0:56:15 > 0:56:18Justin was there when his mother was murdered.
0:56:18 > 0:56:22He's seen everything and he was real devastated.
0:56:22 > 0:56:25You know, he'd just cry a lot
0:56:25 > 0:56:28and scared to go upstairs
0:56:28 > 0:56:30to his room, scared to sleep at night.
0:56:30 > 0:56:35He had to sleep with us, er, he just wasn't Justin again.
0:56:35 > 0:56:38He wasn't a happy child at all, nothing like that again.
0:56:40 > 0:56:42Stand up straight.
0:56:42 > 0:56:45Justin was sent to see Dr Bruce Perry
0:56:45 > 0:56:48who works with children from abusive families.
0:56:48 > 0:56:50You're taller than you were last time you were here.
0:56:53 > 0:56:57I saw him very soon after the event
0:56:57 > 0:57:01and had him come into our office...
0:57:02 > 0:57:08..and just getting at or even mentioning mother
0:57:08 > 0:57:12resulted in this tremendous, explosive,
0:57:12 > 0:57:15what I would consider, re-enactment behaviour.
0:57:19 > 0:57:21And I think in many ways,
0:57:21 > 0:57:24his behaviours were not necessarily re-enactment of the murder,
0:57:24 > 0:57:26but they were re-enactment, I think,
0:57:26 > 0:57:29of the kinds of domestic violence that he had seen prior to that.
0:57:33 > 0:57:34Luckily for Justin,
0:57:34 > 0:57:38he's receiving the help he needs to reverse the damage.
0:57:38 > 0:57:42In the 18 months he's been attending Dr Perry's clinic,
0:57:42 > 0:57:43he's made great progress.
0:57:45 > 0:57:46Back on track.
0:57:46 > 0:57:48It's going to be a slow process
0:57:48 > 0:57:52but his future is going to be real bright, I can see that.
0:58:06 > 0:58:09We know a huge amount about what happens inside the minds
0:58:09 > 0:58:13and brains of murderers that have been caught, but we are still
0:58:13 > 0:58:16some way off being able to predict who will become a murderer.
0:58:16 > 0:58:19There are far too many factors involved.
0:58:19 > 0:58:23One thing, however, is certain, we will continue to be fascinated
0:58:23 > 0:58:27and appalled by their terrible crimes for many years to come.