0:00:04 > 0:00:08In the act of murder, there is a weapon...
0:00:12 > 0:00:13..a crime scene...
0:00:16 > 0:00:17..and a body.
0:00:19 > 0:00:23All vital evidence in the hunt for the killer.
0:00:25 > 0:00:29It's a game of cat and mouse between police and murderer
0:00:29 > 0:00:32that used to favour the criminal.
0:00:32 > 0:00:37But then something happened that swung the odds in favour of justice.
0:00:39 > 0:00:42The arrival of forensic science.
0:00:47 > 0:00:49I'm Gabriel Weston.
0:00:49 > 0:00:51As a surgeon and writer,
0:00:51 > 0:00:55I'm fascinated by the work of the forensic scientist
0:00:55 > 0:00:57and the murders they've helped to solve.
0:01:02 > 0:01:04In this series...
0:01:05 > 0:01:06..I'll explore the cases
0:01:06 > 0:01:09that transformed criminal investigation.
0:01:11 > 0:01:13Through poison and acid...
0:01:15 > 0:01:17..fingerprints and blood.
0:01:19 > 0:01:21From the earliest days
0:01:21 > 0:01:24to the cutting edge of modern forensics.
0:01:26 > 0:01:30In this episode I'll be looking at weapons.
0:01:30 > 0:01:34I'll reveal how fundamental the instrument of murder is
0:01:34 > 0:01:37for catching the criminal and solving the crime.
0:01:38 > 0:01:40There will always be those
0:01:40 > 0:01:43who believe they can commit the perfect murder,
0:01:43 > 0:01:46who think they can wield a weapon
0:01:46 > 0:01:48but conceal their crime.
0:01:48 > 0:01:54This is the story of how forensic science has emerged to thwart them,
0:01:54 > 0:01:57using the murder weapon to catch the killer.
0:02:26 > 0:02:29The year is 1235.
0:02:31 > 0:02:36In a remote part of China, a body is discovered in a field.
0:02:38 > 0:02:41The victim has been hacked to death.
0:02:43 > 0:02:47Distinctive cuts point to a sickle as the murder weapon.
0:02:51 > 0:02:56An investigator called Sung Tzu has the job of finding the killer,
0:02:56 > 0:03:01and he orders everyone in the village who owns a sickle
0:03:01 > 0:03:03to lay it out in the open air.
0:03:12 > 0:03:15At first there's nothing to see.
0:03:20 > 0:03:23But then a fly lands on one of the blades.
0:03:23 > 0:03:28It's soon joined by another, and then, another.
0:03:32 > 0:03:35Attracted by invisible traces of blood,
0:03:35 > 0:03:38the flies reveal the murder weapon,
0:03:38 > 0:03:42and confronted with the evidence, the owner confesses.
0:03:42 > 0:03:45It's the earliest written account we have
0:03:45 > 0:03:49of forensic science being used to identify the murder weapon
0:03:49 > 0:03:51and, hence, the killer.
0:04:00 > 0:04:04Forensics has elevated the murder weapon
0:04:04 > 0:04:06from its role as mere evidence
0:04:06 > 0:04:09to that of key witness.
0:04:09 > 0:04:12But the story of this progress is a dark one,
0:04:12 > 0:04:17complete with hatred, passion, blood and gore.
0:04:17 > 0:04:21And it starts at a time when the most popular weapon
0:04:21 > 0:04:26was routinely being used without being discovered.
0:04:26 > 0:04:29A weapon that left no trace.
0:04:37 > 0:04:40Southwest France, 1840.
0:04:41 > 0:04:4324-year-old Marie Lafarge
0:04:43 > 0:04:47is preparing eggnog for her new husband,
0:04:47 > 0:04:49who has suddenly fallen ill.
0:04:54 > 0:04:57As Marie adds some white powder,
0:04:57 > 0:05:00family friend Anna Brun grows suspicious.
0:05:03 > 0:05:06Marie claims she's simply adding sugar,
0:05:06 > 0:05:09but Anna doesn't believe her.
0:05:09 > 0:05:13She suspects it's poison,
0:05:13 > 0:05:16but she has no way to prove it.
0:05:20 > 0:05:23Marie had been married for just five months.
0:05:23 > 0:05:26She had grown up in affluent Parisian society
0:05:26 > 0:05:31but, when her parents died, she was left with little money.
0:05:31 > 0:05:34When, at the ripe old age of 23,
0:05:34 > 0:05:36she was still unmarried,
0:05:36 > 0:05:40Marie's relatives took matters into their own hands.
0:05:41 > 0:05:44Marie's uncle consulted a marriage broker
0:05:44 > 0:05:47and he selected an eligible bachelor for her,
0:05:47 > 0:05:51a wealthy businessman called Charles Lafarge.
0:05:51 > 0:05:55Now, it's clear that Marie didn't find him at all prepossessing,
0:05:55 > 0:05:59in fact, in her diary she called him exceedingly ugly.
0:05:59 > 0:06:03But she wasn't marrying for love - it was a business deal,
0:06:03 > 0:06:05and she accepted his proposal.
0:06:09 > 0:06:11The day after their wedding,
0:06:11 > 0:06:15the couple travelled south together to Charles' large estate.
0:06:21 > 0:06:27When Marie arrived at her new home she realised she'd been conned.
0:06:27 > 0:06:31She'd been expecting a grand estate with lots of servants.
0:06:31 > 0:06:36What she found instead was a dilapidated house, full of rats.
0:06:36 > 0:06:38Her new husband didn't have any money -
0:06:38 > 0:06:41in fact, he was in serious debt.
0:06:50 > 0:06:52Distraught, Marie locked herself in a room
0:06:52 > 0:06:54and wrote him an impassioned letter,
0:06:54 > 0:06:58begging him to release her from the marriage.
0:07:01 > 0:07:05But Charles refused.
0:07:05 > 0:07:07Marie was trapped.
0:07:09 > 0:07:12In December of 1839,
0:07:12 > 0:07:15Charles travelled to Paris on business.
0:07:17 > 0:07:21Whilst there, he received a surprise parcel from Marie.
0:07:27 > 0:07:30A cake, accompanied by a love letter.
0:07:38 > 0:07:43Soon after eating the cake, Charles fell violently ill.
0:07:47 > 0:07:51He returned home with sickness and a high fever.
0:07:54 > 0:07:59Marie undertook to nurse her husband back to health.
0:07:59 > 0:08:02She even prepared his food.
0:08:02 > 0:08:07But, despite her solicitous attentions, his condition got worse.
0:08:07 > 0:08:09Even the family doctor was at a loss,
0:08:09 > 0:08:13prescribing eggnog in the hope that all that fat and protein
0:08:13 > 0:08:15might build Charles up a bit.
0:08:21 > 0:08:23Marie did what the doctor ordered.
0:08:30 > 0:08:33And it was while she was making the eggnog
0:08:33 > 0:08:36that Anna Brun saw Marie add the white powder.
0:08:37 > 0:08:42Anna didn't believe that the powder was sugar, as Marie claimed,
0:08:42 > 0:08:45so she hid what was left of the eggnog in a cupboard.
0:08:49 > 0:08:52Just two days later, Charles died.
0:08:55 > 0:08:59The nature of his death didn't worry the family doctor,
0:08:59 > 0:09:02but Anna was troubled by what she'd seen.
0:09:02 > 0:09:07She confided in Charles' family and they alerted the police.
0:09:09 > 0:09:12Marie was arrested on suspicion of murder.
0:09:12 > 0:09:14But suspicion was all it could be,
0:09:14 > 0:09:18because there was no evidence that she'd poisoned her husband.
0:09:18 > 0:09:21Nothing to suggest that any crime had been committed.
0:09:30 > 0:09:33In those days, poison was the weapon of choice.
0:09:35 > 0:09:37And one poison above all.
0:09:38 > 0:09:40Arsenic.
0:09:41 > 0:09:46Arsenic was sold at most hardware stores as a way to control rats.
0:09:47 > 0:09:49It was an odourless powder
0:09:49 > 0:09:52that caused symptoms common to many natural diseases.
0:09:55 > 0:09:57Arsenic was a popular weapon,
0:09:57 > 0:10:01precisely because it was impossible to detect.
0:10:01 > 0:10:04You might have suspicions that someone had been poisoned,
0:10:04 > 0:10:07but there was no way of proving it.
0:10:07 > 0:10:09But all that was about to change.
0:10:12 > 0:10:16In 1836, four years before Marie was arrested,
0:10:16 > 0:10:19a Scottish chemist called James Marsh
0:10:19 > 0:10:23had invented a test to detect the presence of arsenic.
0:10:25 > 0:10:29The lawyers prosecuting Marie had heard of the Marsh test
0:10:29 > 0:10:34and wanted to use it to prove she'd poisoned Charles.
0:10:34 > 0:10:37They asked the judge if a toxicologist could be summoned
0:10:37 > 0:10:40to test the leftover eggnog
0:10:40 > 0:10:42and samples of Charles' organs.
0:10:42 > 0:10:44The judge agreed
0:10:44 > 0:10:47and called for the world's leading toxicologist
0:10:47 > 0:10:50to be brought before the court.
0:10:50 > 0:10:52His name was Mathieu Orfila.
0:10:54 > 0:10:57In front of a crowded courtroom,
0:10:57 > 0:10:59he set to work on Charles' organs.
0:11:08 > 0:11:11Here at University College London,
0:11:11 > 0:11:15Professor Andrea Sella is going to recreate what he did
0:11:16 > 0:11:21So, Andrea, can you show me what the Marsh test consists of
0:11:21 > 0:11:22and how to do it?
0:11:22 > 0:11:25Well, the Marsh test is a really beautiful chemical test.
0:11:25 > 0:11:28We're going to take some zinc
0:11:28 > 0:11:30and put it into our flask here.
0:11:32 > 0:11:35And the second step is simply going to be
0:11:35 > 0:11:38to pour some sulphuric acid.
0:11:39 > 0:11:42- You can see down at the bottom... - You can see the bubbles coming up.
0:11:42 > 0:11:45..that there are bubbles beginning to come up.
0:11:46 > 0:11:48So, what do we do next, Andrea?
0:11:48 > 0:11:50Now things get dangerous,
0:11:50 > 0:11:54and that means that we can't have it out here in the open.
0:11:55 > 0:11:57'Next, we add our sample.
0:11:57 > 0:12:01'A piece of lamb's liver, sprinkled with arsenic.'
0:12:01 > 0:12:04And so I'll take the stopper off a tiny bit
0:12:04 > 0:12:06and then if you just drop it in there.
0:12:09 > 0:12:10If the test works,
0:12:10 > 0:12:12the arsenic will react
0:12:12 > 0:12:16to produce a highly toxic gas called arsine.
0:12:17 > 0:12:19I think we've waited long enough -
0:12:19 > 0:12:22this is fizzing quite intensely.
0:12:22 > 0:12:25To test for the presence of arsine
0:12:25 > 0:12:26and, hence, arsenic,
0:12:26 > 0:12:30all you need is a piece of porcelain.
0:12:30 > 0:12:32What I'd like you to do is to reach into the fume hood
0:12:32 > 0:12:36and very carefully put the dish just above the flame.
0:12:38 > 0:12:40If arsine is present,
0:12:40 > 0:12:44a black mark will appear on the porcelain.
0:12:44 > 0:12:46Just close enough, right into the glow.
0:12:49 > 0:12:51And there is the spot.
0:12:51 > 0:12:53Look at that.
0:12:53 > 0:12:58As the arsine burns, then the arsine is converted back to arsenic metal
0:12:58 > 0:13:00and you get that black spot.
0:13:00 > 0:13:03So that is a perfectly positive Marsh test.
0:13:03 > 0:13:06And so this is a completely positive Marsh test.
0:13:07 > 0:13:08'Back in 1840,
0:13:08 > 0:13:12'when Orfila held the porcelain up to the flame,
0:13:12 > 0:13:16'the courtroom was packed with spectators.'
0:13:16 > 0:13:20That audience would have been waiting with bated breath
0:13:20 > 0:13:22to find out if this woman,
0:13:22 > 0:13:26who claimed that she was innocent, had indeed poisoned her husband.
0:13:26 > 0:13:28This is really chemistry as a spectator sport.
0:13:28 > 0:13:29And in this case,
0:13:29 > 0:13:33there's something really kind of voyeuristic and salacious about it,
0:13:33 > 0:13:36because what you know is that, you know,
0:13:36 > 0:13:41in a sense the life of someone hangs on this... This one test.
0:13:41 > 0:13:44And in front of the expectant crowd,
0:13:44 > 0:13:47the cause of Charles Lafarge's death slowly emerged
0:13:47 > 0:13:50on a piece of white porcelain.
0:13:55 > 0:13:57There was no longer any doubt.
0:13:57 > 0:13:59He'd been poisoned.
0:14:01 > 0:14:05Marie was found guilty and sentenced to life imprisonment.
0:14:06 > 0:14:09In the autobiography she wrote in prison,
0:14:09 > 0:14:11she continued to protest her innocence,
0:14:11 > 0:14:14saying that Charles had been poisoned by his family,
0:14:14 > 0:14:17the arsenic put in his eggnog to frame her.
0:14:18 > 0:14:22Public opinion was certainly divided at the time,
0:14:22 > 0:14:25but while the identity of the murderer
0:14:25 > 0:14:27might have been endlessly contested,
0:14:27 > 0:14:30that of the murder weapon itself was not.
0:14:30 > 0:14:34Charles had been poisoned by arsenic.
0:14:34 > 0:14:36The Marsh test had proved it.
0:14:46 > 0:14:50Today, forensic chemistry can reveal far more
0:14:50 > 0:14:53than the mere presence of a poison.
0:14:53 > 0:14:57It can scrutinise the very atoms of the human body
0:14:57 > 0:15:01and reveal truths that a criminal may want to hide.
0:15:07 > 0:15:10At the forefront of exciting new research
0:15:10 > 0:15:13is Doctor Stuart Black from the University of Reading.
0:15:17 > 0:15:21A few weeks ago, I sent off a few strands of my hair to Stuart,
0:15:21 > 0:15:25and now I'm here to find out what, if anything,
0:15:25 > 0:15:27my hair reveals about me.
0:15:35 > 0:15:38So, Stuart, what did you find in my hair?
0:15:38 > 0:15:40OK, well, what we've analysed here
0:15:40 > 0:15:42is the different elements in your hair,
0:15:42 > 0:15:44just everyday elements on the periodic table.
0:15:44 > 0:15:47Some are quite rare, in cases,
0:15:47 > 0:15:49but some are not there in large abundance.
0:15:49 > 0:15:51Things like strontium, lead,
0:15:51 > 0:15:55these are elements that occur naturally in food, in water,
0:15:55 > 0:15:57in the dust that we're breathing in -
0:15:57 > 0:16:00and these accumulate in our hair as we ingest them.
0:16:02 > 0:16:04Surprisingly, we all have traces
0:16:04 > 0:16:07of metals like strontium and lead in our hair.
0:16:07 > 0:16:11And there's something about these elements
0:16:11 > 0:16:14that can reveal unique details about us as individuals.
0:16:14 > 0:16:20It all hinges on the fact they have atoms with different weights -
0:16:20 > 0:16:22known as isotopes.
0:16:22 > 0:16:26So if we take lead, for example, it has lots of different isotopes.
0:16:26 > 0:16:30There's a lead called 208 lead, 207 lead and 206 lead.
0:16:30 > 0:16:32Now, in forensics,
0:16:32 > 0:16:36the important thing is that different isotopes
0:16:36 > 0:16:38occur in different places.
0:16:39 > 0:16:42This means that isotopes in someone's hair
0:16:42 > 0:16:44can reveal where they've been.
0:16:45 > 0:16:48Recently, I travelled to Australia.
0:16:48 > 0:16:53So now I want to know whether Stuart has been able to work that out
0:16:53 > 0:16:57just from analysing strands of my hair.
0:17:00 > 0:17:03So if we look at the map of strontium isotopes on the globe,
0:17:03 > 0:17:05we're looking for values
0:17:05 > 0:17:09somewhere in this sort of purpley, dark-blue area.
0:17:09 > 0:17:12Now, that focuses on parts of Canada and the US,
0:17:12 > 0:17:14very, very northern parts of Scandinavia,
0:17:14 > 0:17:18Asia, Australia, and parts of Africa as well.
0:17:18 > 0:17:21And if you were conducting this from a forensic point of view,
0:17:21 > 0:17:22is there any other way
0:17:22 > 0:17:25that you could sort of locate me more specifically than that?
0:17:25 > 0:17:29Yeah, the way to improve that sort of precision on the data
0:17:29 > 0:17:32is to then look at another isotope ratio,
0:17:32 > 0:17:36and the lead isotope ratios for your hair samples
0:17:36 > 0:17:37are these yellowy dots.
0:17:37 > 0:17:40This the part where you hadn't particularly travelled very far,
0:17:40 > 0:17:44and that plots it nicely in the European field.
0:17:44 > 0:17:46And then these other two areas up here
0:17:46 > 0:17:47plot quite close into this area
0:17:47 > 0:17:50which overlaps with the UK and Australia.
0:17:50 > 0:17:52And, of course, Australia was one of the areas
0:17:52 > 0:17:54in which the strontium sort of...
0:17:54 > 0:17:55It certainly was.
0:17:55 > 0:17:57So my bet would be you've been to Australia.
0:17:57 > 0:17:58I have. I have.
0:17:58 > 0:18:02That is amazing, that you've managed to quite correctly locate me.
0:18:02 > 0:18:06We were there for three weeks over Christmas, so, my goodness.
0:18:06 > 0:18:10So the criminal needs to watch out, don't they?
0:18:10 > 0:18:13Now, where in Australia is a bit of a difficult question.
0:18:13 > 0:18:15Do you want to hazard a guess, Stuart?
0:18:15 > 0:18:16Well, the ones that are closest
0:18:16 > 0:18:19are perhaps southern and parts of southeast Australia,
0:18:19 > 0:18:21those are the closest areas.
0:18:21 > 0:18:22Bang on. Absolutely bang on.
0:18:22 > 0:18:26So, I was on the Mornington Peninsula.
0:18:26 > 0:18:28So, look at that - absolutely fantastic.
0:18:28 > 0:18:29That's good.
0:18:29 > 0:18:34Isotope analysis can reveal suspects' recent movements,
0:18:34 > 0:18:36which they may be trying to hide.
0:18:37 > 0:18:39It can destroy alibis
0:18:39 > 0:18:41and expose lies.
0:18:43 > 0:18:48It's amazing to think that a criminal can now be betrayed
0:18:48 > 0:18:50by the very hair on their head.
0:18:52 > 0:18:55Forensic chemistry has come a long way
0:18:55 > 0:18:59since the Marsh test was used to convict Marie Lafarge.
0:19:01 > 0:19:04Today, toxicology is a routine part
0:19:04 > 0:19:06of every murder case.
0:19:07 > 0:19:11But when it was first developed back in the 19th century,
0:19:11 > 0:19:16it completely changed the way that deaths were investigated.
0:19:16 > 0:19:19What might initially be thought of as a natural death
0:19:19 > 0:19:24could be revealed as a murder with one simple scientific test.
0:19:24 > 0:19:29Poison was no longer easy to disguise.
0:19:29 > 0:19:32Forensics could expose it as the murder weapon.
0:19:37 > 0:19:40By the start of the 20th century,
0:19:40 > 0:19:43poison had fallen out of fashion.
0:19:43 > 0:19:46A new kind of weapon was becoming popular.
0:19:46 > 0:19:48It killed quickly,
0:19:48 > 0:19:49could be easily concealed,
0:19:49 > 0:19:52and could be used at a distance.
0:19:57 > 0:19:58The gun.
0:20:02 > 0:20:04Guns had been expensive.
0:20:08 > 0:20:12It was only the shooting and hunting classes who could afford them.
0:20:12 > 0:20:15But when men returned from the First World War,
0:20:15 > 0:20:18their firearms often came home with them.
0:20:19 > 0:20:22Guns weren't just an easy way of killing,
0:20:22 > 0:20:25they had another distinct advantage -
0:20:25 > 0:20:27they were anonymous.
0:20:27 > 0:20:30Detectives turning up at a crime scene
0:20:30 > 0:20:32might be able to tell that a gun had been used,
0:20:32 > 0:20:37but there was no way of working out which gun was the murder weapon.
0:20:37 > 0:20:40But one high-profile murder case
0:20:40 > 0:20:44would strip guns of their anonymity forever.
0:20:46 > 0:20:49On the 20th of January 1928,
0:20:49 > 0:20:53police arrested petty criminal Frederick Browne
0:20:53 > 0:20:54on suspicion of robbery.
0:20:56 > 0:20:59But when the police searched his property,
0:20:59 > 0:21:03they found something unexpected.
0:21:03 > 0:21:05A kind of revolver called a Webley.
0:21:06 > 0:21:08They were astonished.
0:21:08 > 0:21:11For four months they'd been searching all over the country
0:21:11 > 0:21:13for a Webley revolver
0:21:13 > 0:21:17in connection with the violent murder of one of their colleagues.
0:21:17 > 0:21:22And now one had turned up right under their noses.
0:21:22 > 0:21:24But was it the murder weapon?
0:21:26 > 0:21:29The crime had taken place four months earlier,
0:21:29 > 0:21:33near the village of Stapleford Abbotts in rural Essex.
0:21:34 > 0:21:36The local constable, PC Gutteridge,
0:21:36 > 0:21:39was walking home after his night shift
0:21:39 > 0:21:42when he heard a car approaching.
0:21:43 > 0:21:46A car driving along a remote country lane
0:21:46 > 0:21:50in the early hours of the morning was unusual in the 1920s.
0:21:50 > 0:21:54Unusual enough for PC Gutteridge to flag it down.
0:22:02 > 0:22:05It would be the last thing he ever did.
0:22:12 > 0:22:14About 6am the next morning,
0:22:14 > 0:22:18the local postman discovered PC Gutteridge
0:22:18 > 0:22:21lying by the side of the road.
0:22:21 > 0:22:23He'd been shot four times -
0:22:23 > 0:22:26two bullets to the left side of the face,
0:22:26 > 0:22:27one in each eye.
0:22:27 > 0:22:30Now, there's something about this murder
0:22:30 > 0:22:32that feels particularly horrible,
0:22:32 > 0:22:34but there was a superstition at the time
0:22:34 > 0:22:37that the last thing a person sees
0:22:37 > 0:22:39gets imprinted on their retinas.
0:22:39 > 0:22:43The killer was trying to avoid being identified.
0:22:55 > 0:22:59At 7:45am, Detective Inspector Crockford arrived
0:22:59 > 0:23:02and examined the murder scene.
0:23:08 > 0:23:11It was clear that PC Gutteridge had been about to take notes
0:23:11 > 0:23:13when he was shot.
0:23:14 > 0:23:17Crockford suspected he'd flagged down a car.
0:23:21 > 0:23:22And before long,
0:23:22 > 0:23:25he discovered that a car had been stolen earlier that night
0:23:25 > 0:23:29from a house just ten miles away from the murder scene.
0:23:35 > 0:23:38It was found the following morning, abandoned.
0:23:40 > 0:23:43There were traces of blood on the bodywork.
0:23:44 > 0:23:46And its mudguard had been damaged.
0:23:50 > 0:23:54Discarded on the floor was a gun cartridge.
0:23:54 > 0:23:59Detectives were convinced it had come from the murder weapon,
0:23:59 > 0:24:01so could the cartridge lead them to the gun?
0:24:03 > 0:24:05The police sent the cartridge
0:24:05 > 0:24:07to the one man who might be able to help them -
0:24:07 > 0:24:10Robert Churchill, the foremost expert
0:24:10 > 0:24:14in the up-and-coming science of ballistics.
0:24:16 > 0:24:18Churchill recognised the cartridge
0:24:18 > 0:24:20as coming from a Webley revolver,
0:24:20 > 0:24:23but that didn't get them much further -
0:24:23 > 0:24:27the Webley was a very common weapon in the 1920s.
0:24:28 > 0:24:31He examined the cartridge under the microscope,
0:24:31 > 0:24:34looking for anything that could narrow down the search.
0:24:36 > 0:24:38He discovered a curious mark,
0:24:38 > 0:24:41a tiny imperfection shaped like a jockey's cap.
0:24:44 > 0:24:46Anyone else might have overlooked it,
0:24:46 > 0:24:50but Churchill knew instantly it was an important clue.
0:24:52 > 0:24:55Four months later, when the police discovered the Webley revolver
0:24:55 > 0:24:57in Robert Browne's possession,
0:24:57 > 0:25:01Churchill knew this could be the breakthrough he'd been waiting for.
0:25:03 > 0:25:07If he could establish a match between this gun and the cartridge,
0:25:07 > 0:25:10he'd have found the murder weapon.
0:25:15 > 0:25:17And to discover what he did next,
0:25:17 > 0:25:21I've come to the National Ballistics Intelligence Service
0:25:21 > 0:25:24to meet forensic ballistics expert Martin Parker.
0:25:26 > 0:25:29The first step is to fire the gun,
0:25:29 > 0:25:31and Martin has an original Webley.
0:25:34 > 0:25:37It will be a new experience for me.
0:25:37 > 0:25:38I've never fired a gun before.
0:25:43 > 0:25:45So, I'm just going to get in position.
0:25:45 > 0:25:48That's it. Keep it pointing, just a bit lower. That's it.
0:25:50 > 0:25:52- What do you think? - That's a good position. OK.
0:25:58 > 0:25:59Whew!
0:25:59 > 0:26:01OK. Just open the gun now.
0:26:01 > 0:26:05Feels nice. Got to tell you. Smells nice, too.
0:26:07 > 0:26:09OK, so just push down on the stirrup latch.
0:26:11 > 0:26:14- And that's it. - That's the cartridge?- It's ejected.
0:26:16 > 0:26:20To establish a match between a cartridge and a gun,
0:26:20 > 0:26:23what's crucial is what happens inside the gun
0:26:23 > 0:26:25at the instant it's fired.
0:26:29 > 0:26:31When the bullet's fired...
0:26:32 > 0:26:35..there is very high pressure inside the cartridge case,
0:26:35 > 0:26:38and that takes an imprint of this steel breech face
0:26:38 > 0:26:39because this is a soft metal.
0:26:39 > 0:26:41So, anything in this area
0:26:41 > 0:26:45can leave markings on the cartridge case,
0:26:45 > 0:26:46and those markings will be unique.
0:26:50 > 0:26:52'm going to compare my cartridge
0:26:52 > 0:26:54with another one fired from the same gun
0:26:54 > 0:26:57using what's called a comparison microscope.
0:26:59 > 0:27:02It allows you to examine two cartridges at once.
0:27:07 > 0:27:09So, you've sort of overlaid one on the other...
0:27:09 > 0:27:13- So that they should line up. - ..to make it incredibly easy for me.
0:27:13 > 0:27:15So I can... I mean, I can definitely see it now.
0:27:16 > 0:27:19Magnified and placed side by side,
0:27:19 > 0:27:23it's easy to see that the two cartridges have identical lines.
0:27:25 > 0:27:29These are caused by tiny imperfections inside the gun
0:27:29 > 0:27:33created during the manufacturing process.
0:27:33 > 0:27:36No two guns have the same imperfections,
0:27:36 > 0:27:39so every time a gun is fired
0:27:39 > 0:27:43it leaves its own unique imprint on the cartridge.
0:27:44 > 0:27:46Such as the jockey-cap mark
0:27:46 > 0:27:51that Churchill noticed on the cartridge found in the stolen car.
0:27:52 > 0:27:55When Churchill fired Browne's gun
0:27:55 > 0:27:57and examined the cartridge
0:27:57 > 0:28:01he observed the same unique jockey-cap mark
0:28:01 > 0:28:03and was able to tell the police
0:28:03 > 0:28:07that Frederick Browne's gun was indeed the murder weapon.
0:28:09 > 0:28:11But Browne claimed he was innocent.
0:28:11 > 0:28:14He said a colleague of his, called Kennedy,
0:28:14 > 0:28:18had given him the gun after the murder and not before.
0:28:20 > 0:28:23When police arrived to arrest Kennedy
0:28:23 > 0:28:25he drew a gun and tried to fire.
0:28:30 > 0:28:32Luckily, the safety catch was on.
0:28:37 > 0:28:42Both Browne and Kennedy were sent for trial at the Old Bailey.
0:28:43 > 0:28:45Back in 1928,
0:28:45 > 0:28:49the science of ballistics was unfamiliar territory for a jury.
0:28:49 > 0:28:53Churchill presented photos of the jockey-cap mark
0:28:53 > 0:28:56on the cartridge found in the stolen car
0:28:56 > 0:28:59and also of the matching imperfection
0:28:59 > 0:29:03inside the Webley found in Brown's possession.
0:29:03 > 0:29:06His evidence was compelling.
0:29:06 > 0:29:08The jury found both men guilty.
0:29:11 > 0:29:13Kennedy and Browne were hanged.
0:29:18 > 0:29:23The most eloquent witness had been the cartridge.
0:29:23 > 0:29:26It had led the police to the murder weapon
0:29:26 > 0:29:27and, hence, the killer.
0:29:27 > 0:29:32The case of the jockey-cap killer put ballistics on the map.
0:29:32 > 0:29:35For the very first time in an English court,
0:29:35 > 0:29:38firearms evidence had been used
0:29:38 > 0:29:40to secure a murder conviction.
0:29:47 > 0:29:51Guns were no longer an anonymous way to kill.
0:29:53 > 0:29:55SIREN WAILS
0:29:59 > 0:30:03As forensic techniques have advanced, so have the criminals.
0:30:03 > 0:30:08Nowadays, many would know not to leave bullets at a crime scene.
0:30:08 > 0:30:11But in their quest to stay one step ahead,
0:30:11 > 0:30:16ballistics experts are now using an exciting new piece of kit.
0:30:18 > 0:30:21To show me how it works,
0:30:21 > 0:30:23crime-scene analyst Mark DeGiovanni
0:30:23 > 0:30:25has recreated the scene of a murder.
0:30:26 > 0:30:31It's the case of US police officer Deputy Sheriff Jose Diaz,
0:30:31 > 0:30:33who was shot and killed.
0:30:33 > 0:30:37The gunman claimed that he had fired in self-defence
0:30:37 > 0:30:39after Diaz had pulled his gun.
0:30:39 > 0:30:42The case rested on whether his account was true.
0:30:44 > 0:30:46And Mark has a piece of technology
0:30:46 > 0:30:49that can help discover what really happened.
0:30:51 > 0:30:52Firstly, what we have to do
0:30:52 > 0:30:55is carry out what we call a laser-scan survey.
0:30:55 > 0:30:59The 3-D scanner sends out lasers in all directions
0:30:59 > 0:31:02to gather the detail of its surroundings
0:31:02 > 0:31:05and build a virtual model of the scene.
0:31:06 > 0:31:10In the Diaz case, the investigators used the virtual model
0:31:10 > 0:31:13to work out the position of the gunman.
0:31:13 > 0:31:14From bullet marks on the car,
0:31:14 > 0:31:18they were able to recreate the trajectory of the bullet.
0:31:18 > 0:31:21So, we don't get a straight line coming out of it,
0:31:21 > 0:31:24we get a small cone with about a five-degree error
0:31:24 > 0:31:28and we can see how that cone projects outwards into the scene.
0:31:32 > 0:31:35They were able to prove that he was 70 metres away, behind a wall.
0:31:36 > 0:31:38But the position of the gunman
0:31:38 > 0:31:41didn't tell them whether he'd fired in self-defence.
0:31:43 > 0:31:48The main issue in the Diaz case was actually the position of the victim.
0:31:49 > 0:31:54To work out the position Diaz was in the moment he was shot,
0:31:54 > 0:31:56Mark introduces a model of the body
0:31:56 > 0:32:00with the exact path the bullet took through it.
0:32:00 > 0:32:02What we're going to do is just bring them together
0:32:02 > 0:32:05and analyse the two as one, really.
0:32:05 > 0:32:08So, you have to get the body into a position
0:32:08 > 0:32:12that realistically could have had a bullet enter it at that angle?
0:32:12 > 0:32:13Absolutely.
0:32:16 > 0:32:21The body is manoeuvred in the scene until the two lines of trajectory,
0:32:21 > 0:32:25one through the body and one through the crime scene, line up.
0:32:27 > 0:32:29Diaz was trying to take cover
0:32:29 > 0:32:32and he was trying to sort of make himself as small as possible.
0:32:32 > 0:32:35So this really does show conclusively
0:32:35 > 0:32:39that this is the only position that he could have been at
0:32:39 > 0:32:41in order for that bullet to have made sense, as it were.
0:32:41 > 0:32:42Absolutely.
0:32:43 > 0:32:46The 3-D laser scanner helped prove
0:32:46 > 0:32:50that Diaz had been crouching when he was shot.
0:32:50 > 0:32:52The suspect was charged with murder.
0:32:55 > 0:32:58Thanks to 3-D laser scanning,
0:32:58 > 0:33:02ballistics experts no longer need the bullet or cartridge
0:33:02 > 0:33:05because they can piece together exactly what happened
0:33:05 > 0:33:08simply from traces, like bullet holes,
0:33:08 > 0:33:10that the weapon leaves behind.
0:33:12 > 0:33:15But some investigators don't even have that much to go on,
0:33:15 > 0:33:18because not all weapons leave a mark.
0:33:18 > 0:33:21In fact, there's one that doesn't create evidence
0:33:21 > 0:33:23so much as destroying it,
0:33:23 > 0:33:27and it's something that most of us wouldn't even think of as a weapon.
0:33:32 > 0:33:34Fire.
0:33:36 > 0:33:38Arson is a brutal crime.
0:33:39 > 0:33:44It's used to destroy property and, occasionally, to kill.
0:33:47 > 0:33:49But fire is a risky weapon.
0:33:49 > 0:33:52It's impossible to control.
0:33:53 > 0:33:55It has a life of its own.
0:33:59 > 0:34:01Yet, for a potential murderer,
0:34:01 > 0:34:04fire has an important advantage.
0:34:07 > 0:34:09It can be made to look like an accident.
0:34:17 > 0:34:20John Lentini is an expert fire investigator.
0:34:21 > 0:34:25In 1990, he received a call from the prosecutor's office
0:34:25 > 0:34:28in Jacksonville, Florida.
0:34:28 > 0:34:30They needed his help with a tragic case.
0:34:33 > 0:34:37There was a fire in October of 1990...
0:34:38 > 0:34:40..in which six people died.
0:34:41 > 0:34:45Mrs Lewis, Mrs Lewis' sister,
0:34:45 > 0:34:47and her sister's four children.
0:34:47 > 0:34:50Mr Lewis, Gerald Lewis, survived,
0:34:50 > 0:34:52as did his four-year-old son.
0:34:52 > 0:34:55That was his only blood relative in the house.
0:34:55 > 0:34:58SIRENS WAIL
0:34:58 > 0:35:01Gerald Lewis had a court order to stay away from his wife,
0:35:01 > 0:35:04and they had had a very rocky relationship
0:35:04 > 0:35:06over the last six months.
0:35:06 > 0:35:08So, yeah, he was the obvious suspect.
0:35:08 > 0:35:11And in any fire like this,
0:35:11 > 0:35:14where you survive and everybody else dies,
0:35:14 > 0:35:16the survivor is the suspect.
0:35:17 > 0:35:20So tell me about the position that he was in
0:35:20 > 0:35:22at the time that you were called in.
0:35:22 > 0:35:25Well, he was a defendant in a capital murder case.
0:35:25 > 0:35:28He was charged with six counts of felony murder
0:35:28 > 0:35:33and they wanted to send him to the electric chair at Raiford Prison.
0:35:33 > 0:35:37Back in those days, Florida had this device called Old Sparky,
0:35:37 > 0:35:39and they used it quite often.
0:35:39 > 0:35:42And I was retained
0:35:42 > 0:35:46to help Mr Lewis on his way to Old Sparky.
0:35:47 > 0:35:50But Gerald Lewis had a defence.
0:35:50 > 0:35:54He claimed that his young son had started the fire accidentally
0:35:54 > 0:35:58while playing with a lighter next to the sofa.
0:35:58 > 0:36:02So the jury were faced with one key question.
0:36:02 > 0:36:06Was the fire an accident, or was it arson?
0:36:07 > 0:36:10There's one piece of evidence that strongly implies
0:36:10 > 0:36:13that a fire was started deliberately -
0:36:13 > 0:36:15the presence of accelerant,
0:36:15 > 0:36:20a substance like petrol or diesel that can be used to start a fire.
0:36:21 > 0:36:25In the wreckage, fire investigators found clues
0:36:25 > 0:36:27which, at the time, were considered proof
0:36:27 > 0:36:29that an accelerant had been used -
0:36:29 > 0:36:33charring on wood and distinctive marks on the carpet
0:36:33 > 0:36:35known as pour patterns.
0:36:37 > 0:36:40But while these patterns all pointed towards arson,
0:36:40 > 0:36:44one vital piece of evidence was entirely absent.
0:36:45 > 0:36:48There were no traces of accelerant at the scene.
0:36:51 > 0:36:54There was no gasoline found in any of the samples.
0:36:54 > 0:36:59In this context, a negative finding is an inconclusive.
0:36:59 > 0:37:04So, at that point the prosecutor said, well, that kind of hurts,
0:37:04 > 0:37:08and they wanted a second evaluation of the fire-scene inspection.
0:37:11 > 0:37:13This was a high-profile case
0:37:13 > 0:37:16and Gerald's life rested on the result.
0:37:18 > 0:37:20We needed better evidence than what we had,
0:37:20 > 0:37:23and the prosecutors agreed with that, they needed better evidence.
0:37:23 > 0:37:26And so we were... We set up this test fire.
0:37:26 > 0:37:31Lentini set out to test Gerald's story that the fire was an accident.
0:37:32 > 0:37:35He recreated the scene in an abandoned house
0:37:35 > 0:37:37identical to the Lewis home.
0:37:37 > 0:37:41His idea was to set the fire going without accelerant,
0:37:41 > 0:37:45just as Gerald claimed had happened on the night of the blaze.
0:37:47 > 0:37:50Lentini expected the fire would burn far more slowly
0:37:50 > 0:37:54and wouldn't produce any of the charring or pour patterns
0:37:54 > 0:37:56found at the scene of the tragedy.
0:37:58 > 0:38:02And this would establish it must have been arson.
0:38:06 > 0:38:09But the test fire didn't go as anyone expected.
0:38:09 > 0:38:11To reveal what happened,
0:38:11 > 0:38:14I'm going to set up my own.
0:38:15 > 0:38:18I'm with the Scottish Fire and Rescue Service
0:38:18 > 0:38:21at this training facility in Edinburgh,
0:38:21 > 0:38:25and we're going to carry out the controlled burn that Lentini did.
0:38:25 > 0:38:26The difference is
0:38:26 > 0:38:31that we're going to be using this specially designed hot-fire unit.
0:38:35 > 0:38:38Helping me set the scene is Dr Rory Hadden,
0:38:38 > 0:38:40a lecturer in fire investigation
0:38:40 > 0:38:43from the University of Edinburgh.
0:38:43 > 0:38:46We're mocking up a living room, as Lentini did.
0:38:50 > 0:38:53With the room furnished and decorated
0:38:53 > 0:38:55just as it had been before the blaze,
0:38:55 > 0:38:59Lentini took a lighter and set fire to the sofa
0:38:59 > 0:39:03just as Gerald claimed his son had done.
0:39:03 > 0:39:05Lentini used no accelerant,
0:39:05 > 0:39:07he poured no petrol on the floor.
0:39:07 > 0:39:13The fire was started using a single, naked flame.
0:39:14 > 0:39:18And then they watched to see what would happen.
0:39:34 > 0:39:37It's actually burning quite clean in the beginning, but I can...
0:39:37 > 0:39:38You can just make out now
0:39:38 > 0:39:41- there's some kind of black smoke coming off?- Yes, yes.
0:39:50 > 0:39:51We're waiting to see
0:39:51 > 0:39:55whether our fire will reach a crucial transition point
0:39:55 > 0:39:56known as flashover.
0:39:58 > 0:40:01The moment it goes from a fire in a room
0:40:01 > 0:40:03to a room on fire.
0:40:06 > 0:40:07Suddenly really scary, isn't it?
0:40:07 > 0:40:10We can feel it, we're getting very close to flashover.
0:40:12 > 0:40:16You can see that the coffee table has spontaneously ignited.
0:40:17 > 0:40:21Flammable gases released from the furniture ignite,
0:40:21 > 0:40:23filling the room with flames.
0:40:23 > 0:40:27You can see you have the flames that are now coming outside of the room.
0:40:27 > 0:40:30- That is a terrifying scene now.- You can see how quickly that's grown.
0:40:30 > 0:40:33This is for sure flashover, flashover has definitely happened.
0:40:39 > 0:40:40Everything in that room is burning.
0:40:40 > 0:40:43There's nowhere that you can be safe from that fire.
0:40:56 > 0:41:01Back in 1990 when Lentini carried out his test burn,
0:41:01 > 0:41:03the time a fire takes to reach flashover
0:41:03 > 0:41:05was thought to be vital evidence.
0:41:05 > 0:41:11Everyone believed that only a fire started using accelerant
0:41:11 > 0:41:13could get to flashover quickly,
0:41:13 > 0:41:15within a few minutes.
0:41:15 > 0:41:19Without accelerant, they thought it would take much longer -
0:41:19 > 0:41:21at least 15 minutes.
0:41:23 > 0:41:28But the test burn defied all their expectations.
0:41:28 > 0:41:31About three and a half minutes after we set the couch on fire,
0:41:31 > 0:41:32the room went to flashover.
0:41:32 > 0:41:37And when you observed that flashover was reached in just a few minutes,
0:41:37 > 0:41:41that did what to your expectation of how fire worked?
0:41:41 > 0:41:44It changed my view of what the cause of the fire was.
0:41:44 > 0:41:45It rocked my world
0:41:45 > 0:41:49and it changed my view of how to approach fires.
0:41:51 > 0:41:54The fact that an accidental fire
0:41:54 > 0:41:57could reach flashover in less than four minutes
0:41:57 > 0:41:59was a shocking revelation,
0:41:59 > 0:42:03one that completely overturned our understanding of fire.
0:42:05 > 0:42:07And when Lentini ventured into the wreckage,
0:42:07 > 0:42:11he discovered something else that he didn't expect.
0:42:18 > 0:42:21There are one or two things that are quite interesting,
0:42:21 > 0:42:23and one of them is, for example,
0:42:23 > 0:42:26this charring on the table that we see here.
0:42:26 > 0:42:29It used to be believed that, because this has charred at low level,
0:42:29 > 0:42:32that must mean something was burning at low level,
0:42:32 > 0:42:33particularly an accelerant.
0:42:33 > 0:42:36However, now you see that it's just clearly an effect
0:42:36 > 0:42:38of a post-flashover fire.
0:42:39 > 0:42:42And in front of the bookcase, we find something else.
0:42:43 > 0:42:46We have a patch of clean, almost undamaged carpet,
0:42:46 > 0:42:48surrounded by a very sooty mark,
0:42:48 > 0:42:51and that used to be considered to be evidence
0:42:51 > 0:42:54of an accelerant being used - it's what they call a pour pattern.
0:42:54 > 0:42:57However, as we saw, no accelerants were used
0:42:57 > 0:42:58and we still saw this phenomenon.
0:42:58 > 0:43:02The astonishing results of the test burn
0:43:02 > 0:43:05changed the course of the Lewis case.
0:43:06 > 0:43:09I was scheduled to be put under oath the next day,
0:43:09 > 0:43:14and talk about how Mr Lewis' version of events
0:43:14 > 0:43:16was not correct.
0:43:16 > 0:43:19The prosecutors, by the way, were standing right next to me,
0:43:19 > 0:43:20and I turned to them and I said,
0:43:20 > 0:43:23"I don't think I can give a deposition tomorrow."
0:43:24 > 0:43:27The prosecution dropped the case
0:43:27 > 0:43:29and Gerald Lewis was released.
0:43:31 > 0:43:36This case utterly transformed the way we interpret fire scenes.
0:43:36 > 0:43:40Our beliefs about what was evidence of arson
0:43:40 > 0:43:42were exposed as myths.
0:43:42 > 0:43:46We now had to adopt new ways of investigating fire,
0:43:46 > 0:43:50based not on assumptions but on science.
0:43:51 > 0:43:56The case of Gerald Lewis highlighted just how difficult it is
0:43:56 > 0:43:59to distinguish between an accidental fire
0:43:59 > 0:44:01and one started with accelerant.
0:44:02 > 0:44:06But, today, fire investigators have a new member of the team,
0:44:06 > 0:44:09specially adapted to help.
0:44:11 > 0:44:16Meet Gunner. He's one of Britain's fire-investigation dogs.
0:44:16 > 0:44:20Gunner's a five-year-old Labrador-springer cross.
0:44:20 > 0:44:22He's full of energy.
0:44:22 > 0:44:23Always wants to work.
0:44:27 > 0:44:29Gunner is often called to the scene of a fire
0:44:29 > 0:44:31to search for traces of accelerant.
0:44:33 > 0:44:36In this huge disused bank in Birmingham,
0:44:36 > 0:44:38we're putting Gunner to the test.
0:44:39 > 0:44:43We've added a couple of drops of accelerant to a cigarette end...
0:44:45 > 0:44:46..set it alight...
0:44:49 > 0:44:53..and then hidden the remains in one of the vaults in the basement.
0:44:56 > 0:45:00The question is, will Gunner be able to sniff it out?
0:45:02 > 0:45:04HE WHISTLES
0:45:04 > 0:45:06DOG BARKS
0:45:06 > 0:45:07Steady, steady.
0:45:07 > 0:45:11DOG BARKS
0:45:11 > 0:45:15Clive leads Gunner in a systematic search of the building.
0:45:18 > 0:45:21Gunner has a secret weapon -
0:45:21 > 0:45:22his nose.
0:45:22 > 0:45:27It's some 10,000 times more sensitive than ours.
0:45:27 > 0:45:28Nothing on this floor.
0:45:28 > 0:45:30But what about the basement?
0:45:35 > 0:45:38Suddenly, Gunner makes a beeline for the vault room.
0:45:50 > 0:45:51Success!
0:45:53 > 0:45:54Clever dog.
0:45:55 > 0:45:59Having found the accelerant, he gets his reward - an old tennis ball.
0:46:03 > 0:46:05At the scene of a large fire,
0:46:05 > 0:46:10it's often impossible for humans to find accelerant.
0:46:10 > 0:46:14But dogs like Gunner can detect even minuscule traces.
0:46:14 > 0:46:16They can help identify cases
0:46:16 > 0:46:19in which fire has been harnessed as a weapon.
0:46:26 > 0:46:28Whilst fire is unpredictable,
0:46:28 > 0:46:34the weapon that's most commonly used today is one of deadly precision.
0:46:44 > 0:46:48And one breakthrough case for forensic science happened in 1942.
0:46:52 > 0:46:55On a cold day in November,
0:46:55 > 0:46:58at Witley Army Barracks in Surrey...
0:47:00 > 0:47:02..Private Brown was on cleaning duty.
0:47:04 > 0:47:07He had the unpleasant task of unblocking a drain.
0:47:08 > 0:47:12As he reached down to pull out a wodge of soggy paper,
0:47:12 > 0:47:14his hand fell on the blade of a knife.
0:47:16 > 0:47:19He knew the police were looking for a knife
0:47:19 > 0:47:23in connection with the recent murder of a young woman,
0:47:23 > 0:47:26so he went immediately to hand it in.
0:47:26 > 0:47:30The knife went straight to the pathologist working on the case,
0:47:30 > 0:47:32Keith Simpson.
0:47:35 > 0:47:36When Simpson saw the knife,
0:47:36 > 0:47:39he instantly recognised its significance.
0:47:43 > 0:47:48This is the exact knife that Simpson was given.
0:47:48 > 0:47:50It had been lying in a drain for weeks,
0:47:50 > 0:47:55and so it had no traces of blood or anything else on it.
0:47:55 > 0:47:57To me, holding it in my hand now,
0:47:57 > 0:48:00it's hard to imagine how Simpson would have known
0:48:00 > 0:48:02that this was a murder weapon,
0:48:02 > 0:48:04but he did know that.
0:48:04 > 0:48:06How could he have been so sure?
0:48:09 > 0:48:11Four months earlier,
0:48:11 > 0:48:15a body had been discovered in a common close to the army camp.
0:48:15 > 0:48:18Simpson was called to examine it.
0:48:23 > 0:48:27Simpson smelled the body before he saw it.
0:48:27 > 0:48:30Clearly, it had been there for weeks.
0:48:30 > 0:48:33Three of the fingers had been gnawed off by rats,
0:48:33 > 0:48:36the exposed arm had started to mummify
0:48:36 > 0:48:39and there were maggots everywhere.
0:48:39 > 0:48:40The body was so fragile
0:48:40 > 0:48:44that Simpson insisted on digging it up himself by hand.
0:48:44 > 0:48:47Most of it was unrecognisable,
0:48:47 > 0:48:49but some of the clothing,
0:48:49 > 0:48:53a tatty green and white dress, had survived.
0:48:57 > 0:49:00Simpson gathered the body into a plastic sheet
0:49:00 > 0:49:04to take back to his laboratory at Guy's Hospital.
0:49:05 > 0:49:09Simpson's first question was identity -
0:49:09 > 0:49:11who was the murdered girl?
0:49:11 > 0:49:15He examined X-rays of her skeleton, the pattern of the teeth,
0:49:15 > 0:49:19a few strands of hair and clothing found on her body,
0:49:19 > 0:49:23and they all matched the description of a 19-year-old woman
0:49:23 > 0:49:26who hadn't been seen for some time.
0:49:26 > 0:49:28Her name was Joan Pearl Wolfe.
0:49:30 > 0:49:34Joan had run away from home when she was just 16.
0:49:34 > 0:49:37She left a strict Catholic upbringing
0:49:37 > 0:49:42for a life spent drifting between casual jobs and temporary homes.
0:49:42 > 0:49:44Joan had chosen Surrey
0:49:44 > 0:49:47because of its large Canadian army base.
0:49:47 > 0:49:50She'd been enticed by the freedom and romance
0:49:50 > 0:49:52the foreign soldiers represented.
0:49:54 > 0:49:57Simpson had established her identity -
0:49:57 > 0:50:01now he needed to know how Joan had died.
0:50:01 > 0:50:03There was no doubt it had been a violent attack -
0:50:03 > 0:50:06her skull was in pieces.
0:50:06 > 0:50:08Simpson found 38 major fragments
0:50:08 > 0:50:12that had to be fitted meticulously back together.
0:50:15 > 0:50:18Today, over 70 years later,
0:50:18 > 0:50:20Joan's skull still exists.
0:50:21 > 0:50:24It has been carefully preserved
0:50:24 > 0:50:29and is exactly as it was after Simpson reconstructed it.
0:50:30 > 0:50:34The most striking feature about this skull
0:50:34 > 0:50:38is this enormous hole that's missing from the back of it,
0:50:38 > 0:50:41and the radiating fracture marks which spread out from it.
0:50:41 > 0:50:47And Simpson knew that a single blow from a blunt instrument
0:50:47 > 0:50:50had killed Joan Pearl Wolfe.
0:50:50 > 0:50:52But that's not all that you can see,
0:50:52 > 0:50:58there are also these very curious marks on the skull, little holes.
0:50:58 > 0:51:01There's one here, and another one on the top of the skull here.
0:51:05 > 0:51:08These suggest that not only
0:51:08 > 0:51:12was there a kind of horrible, violent killer blow,
0:51:12 > 0:51:14but also some penetrating injuries
0:51:14 > 0:51:17with a much smaller instrument.
0:51:17 > 0:51:20Now, it's clear, just looking at this skull,
0:51:20 > 0:51:22that a really nasty attack
0:51:22 > 0:51:25took place on this victim.
0:51:27 > 0:51:30Detectives investigating Joan's background
0:51:30 > 0:51:35discovered she'd been engaged to a soldier called August Sangret,
0:51:35 > 0:51:38a French-Canadian of Cree Indian descent.
0:51:41 > 0:51:44He'd built Joan shelters in the woods where they could meet up.
0:51:46 > 0:51:49Inside one of these shelters,
0:51:49 > 0:51:52they found a letter from Joan to Sangret,
0:51:52 > 0:51:55claiming that she was pregnant
0:51:55 > 0:51:57and the child was his.
0:52:00 > 0:52:03Sangret was brought in for questioning
0:52:03 > 0:52:07and proceeded to give one of the longest witness statements
0:52:07 > 0:52:08in criminal history,
0:52:08 > 0:52:11running to over 17,000 words.
0:52:11 > 0:52:14But, despite the excessive detail,
0:52:14 > 0:52:17the police still didn't have enough to arrest him on.
0:52:19 > 0:52:21Back in the laboratory,
0:52:21 > 0:52:26Simpson turned his attention to the marks on Joan's skull.
0:52:26 > 0:52:28It was clear to him
0:52:28 > 0:52:29that they'd been made by a knife.
0:52:29 > 0:52:34Now, these penetrating wounds on the skull aren't just violent,
0:52:34 > 0:52:36they're actually curious -
0:52:36 > 0:52:39they have a little slant in them.
0:52:39 > 0:52:40And this told Simpson
0:52:40 > 0:52:44something about the knife that was used in this crime,
0:52:44 > 0:52:46because what he deduced
0:52:46 > 0:52:48was that the little slants in the bone
0:52:48 > 0:52:51showed that the knife that was used
0:52:51 > 0:52:52needed to be twisted
0:52:52 > 0:52:55before it could be removed from Joan's skull.
0:52:58 > 0:53:02Simpson finally had some important information
0:53:02 > 0:53:04to pass on to the detectives.
0:53:04 > 0:53:08They needed to find an unusual knife with a hooked tip.
0:53:09 > 0:53:11And a few weeks later,
0:53:11 > 0:53:14Private Brown found just such a knife
0:53:14 > 0:53:17hidden in the drains of the army barracks.
0:53:20 > 0:53:25Now detectives needed to establish who the knife belonged to.
0:53:26 > 0:53:29They got a break when an officer from the camp,
0:53:29 > 0:53:32Corporal Harding, recognised its distinctive shape.
0:53:34 > 0:53:37Harding had once been handed the knife as lost property
0:53:37 > 0:53:41and had reunited it with its owner - Sangret.
0:53:46 > 0:53:50In court, when the jury retired to consider their verdict,
0:53:50 > 0:53:54they took the two fundamental pieces of evidence with them -
0:53:54 > 0:53:56the skull and the knife.
0:54:02 > 0:54:05On the 2nd of March 1943,
0:54:05 > 0:54:09the jury delivered their verdict - guilty.
0:54:09 > 0:54:11Sangret was hanged at Wandsworth Prison.
0:54:15 > 0:54:19In the Sangret case, the knife led directly to the killer.
0:54:21 > 0:54:25Today, the latest forensic techniques can use the knife
0:54:25 > 0:54:29to determine more than simply who wielded it -
0:54:29 > 0:54:32they can reveal how it was used,
0:54:32 > 0:54:34a distinction that can be vital.
0:54:34 > 0:54:39A common defence is that a stabbing was accidental.
0:54:39 > 0:54:42The accused claims they slipped with the knife in hand,
0:54:42 > 0:54:45or that the victim fell onto the blade.
0:54:45 > 0:54:49Often, there are no witnesses.
0:54:49 > 0:54:53The jury have little more than the accused's word to go on.
0:54:54 > 0:54:57I've come here to the University of Leicester
0:54:57 > 0:55:00to meet professor Sarah Hainsworth,
0:55:00 > 0:55:03who has developed a test that can help establish
0:55:03 > 0:55:07whether or not the person who's done the stabbing is telling the truth.
0:55:10 > 0:55:14Sarah's expertise as a materials engineer
0:55:14 > 0:55:19is frequently called upon to test a suspect's account of what happened.
0:55:19 > 0:55:21Often, the accused will say
0:55:21 > 0:55:23the knife caused more harm than they intended
0:55:23 > 0:55:27because the knife was particularly sharp.
0:55:27 > 0:55:31So, Sarah has devised a way to test the sharpness of the blade -
0:55:31 > 0:55:33a drop tower.
0:55:35 > 0:55:38So, what we have is a knife mounted here. If I simply release it...
0:55:39 > 0:55:40Urgh! It's horrible!
0:55:42 > 0:55:45Yes, I mean, the impact energy here is quite high
0:55:45 > 0:55:48and the knife has penetrated right the way through this foam block.
0:55:48 > 0:55:51And if you used a different sort of knife,
0:55:51 > 0:55:53would you get a different kind of action?
0:55:53 > 0:55:56So, if we used a knife that was blunter,
0:55:56 > 0:55:58then it wouldn't necessarily penetrate
0:55:58 > 0:56:00to the depth that this knife has.
0:56:00 > 0:56:03Sarah has drop-tested hundreds of knives
0:56:03 > 0:56:09and created a scale of sharpness that's used in UK courts.
0:56:09 > 0:56:13But how sharp the weapon is is only half the story.
0:56:14 > 0:56:16What the police are interested in
0:56:16 > 0:56:19is how much force was used in a particular incident.
0:56:19 > 0:56:21So, how hard was that knife taken
0:56:21 > 0:56:23and pushed into somebody
0:56:23 > 0:56:25to create those injuries?
0:56:27 > 0:56:30So, to measure the force used in stabbing,
0:56:30 > 0:56:33Sarah has built a device called a dynamometer.
0:56:35 > 0:56:38What I'd like you to do now is to do a high-force stab,
0:56:38 > 0:56:41so imagine that you've just had an argument with somebody
0:56:41 > 0:56:42and really mean to stab them.
0:56:42 > 0:56:47- So, sort of stabbing as hard as I can type thing?- As hard as you can.
0:56:47 > 0:56:49So, Richard will give you the countdown.
0:56:49 > 0:56:52OK, in three, two, one, go.
0:56:56 > 0:56:58It's sticking in a bit there.
0:56:58 > 0:57:01Yes, so you've gone through the foam and into the backing slightly
0:57:01 > 0:57:05and that recorded about 37 newtons,
0:57:05 > 0:57:07so not the highest force.
0:57:07 > 0:57:10So, I'm not a natural stabber, then.
0:57:10 > 0:57:12No.
0:57:13 > 0:57:15The greater the force used in a stabbing,
0:57:15 > 0:57:18the less plausible that it could have been an accident.
0:57:18 > 0:57:21So this measurement can help establish
0:57:21 > 0:57:24whether an attacker intended to kill.
0:57:26 > 0:57:32And this is what's driving the advance of modern forensics.
0:57:32 > 0:57:36The latest techniques go beyond the facts of who, where and when.
0:57:37 > 0:57:41They know try to tackle the more challenging questions of how...
0:57:43 > 0:57:46..and why.
0:57:46 > 0:57:51Criminals have always attempted to outwit those who seek justice,
0:57:51 > 0:57:56but forensics is providing them with their biggest challenge yet.
0:57:56 > 0:58:00Whether by analysing the victim's body,
0:58:00 > 0:58:03or the murder weapon, or other forms of evidence,
0:58:03 > 0:58:08forensic science is being used ever more successfully
0:58:08 > 0:58:11to lead detectives directly to the killer.
0:58:20 > 0:58:23Delve deeper with the Open University
0:58:23 > 0:58:27and find out more about the science behind forensics.
0:58:27 > 0:58:31Go to...
0:58:31 > 0:58:34..and follow the links to the Open University.