By Nicola Cook BBC Horizon Most murderers are unaware of even the simplest clues that might give them away. But by thinking like a forensic scientist, is the "perfect" murder possible?
By Nicola Cook BBC Horizon Most murderers are unaware of even the simplest clues that might give them away. But by thinking like a forensic scientist, is the "perfect" murder possible?
The so-called perfect murder - an undetectable crime where the killer gets away scot free - has long been the stuff of mystery fiction.
The so-called perfect murder - an undetectable crime where the killer gets away scot free - has long been the stuff of mystery fiction.
From the icicle to the leg of lamb, authors have strived to come up with more imaginative weapons and crimes than their predecessors. But would any of these ingenious methods work?
From the icicle to the leg of lamb, authors have strived to come up with more imaginative weapons and crimes than their predecessors. But would any of these ingenious methods work?
Staging a death to look like an accident is one of the first things an aspiring murderer might try. But when a pathologist examines the body of the victim they're not just looking for the cause of death.
Staging a death to look like an accident is one of the first things an aspiring murderer might try. But when a pathologist examines the body of the victim they're not just looking for the cause of death.
Other minor injuries - like bruising from a struggle, or scratch marks where a body has been dragged - can reveal a murder.
Other minor injuries - like bruising from a struggle, or scratch marks where a body has been dragged - can reveal a murder.
If you're dumping a body, of course you don't think where's the hypostasis, you just dump the body and run Dr Richard ShepherdPathologist Another important clue is hypostasis. When someone dies their blood pressure falls, and gravity makes the blood pool in those regions of the body closest to the ground. This red staining is clearly visible, and can reveal the position of the body at death.
If you're dumping a body, of course you don't think where's the hypostasis, you just dump the body and run Dr Richard ShepherdPathologist Another important clue is hypostasis. When someone dies their blood pressure falls, and gravity makes the blood pool in those regions of the body closest to the ground. This red staining is clearly visible, and can reveal the position of the body at death.
If a body is found lying on its right-hand side, but the red staining due to hypostasis is down the left-hand side, then the body has clearly been moved.
If a body is found lying on its right-hand side, but the red staining due to hypostasis is down the left-hand side, then the body has clearly been moved.
"It gives us a very important clue," says pathologist Dr Richard Shepherd. "If you're dumping a body, of course you don't think where's the hypostasis, you just dump the body and run."
"It gives us a very important clue," says pathologist Dr Richard Shepherd. "If you're dumping a body, of course you don't think where's the hypostasis, you just dump the body and run."
The body can reveal a lot of secrets, so a number of killers have tried to get rid of their victim's body altogether.
The body can reveal a lot of secrets, so a number of killers have tried to get rid of their victim's body altogether.
Mass graves
Mass graves
In the 1940s the "acid bath murderer" John Haigh attempted to dissolve the bodies of six victims in sulphuric acid. This destroys bones and tissue but it can't digest fats - or plastic.
In the 1940s the "acid bath murderer" John Haigh attempted to dissolve the bodies of six victims in sulphuric acid. This destroys bones and tissue but it can't digest fats - or plastic.
This is how John Haigh was caught. A pair of dentures, a red plastic handbag, and three human gallstones - covered in a layer of fat - were retrieved from the acid sludge found at his workshop.
This is how John Haigh was caught. A pair of dentures, a red plastic handbag, and three human gallstones - covered in a layer of fat - were retrieved from the acid sludge found at his workshop.
One mistake and a killer is caught
One mistake and a killer is caught
Another method of body disposal comes from forensic scientists themselves.
Another method of body disposal comes from forensic scientists themselves.
DNA expert Eleanor Graham at the University of Leicester says: "It was developed for situations like the mass graves in Bosnia Herzegovina, where you find mostly skeletonised remains, but a bit of soft tissue adhering.
DNA expert Eleanor Graham at the University of Leicester says: "It was developed for situations like the mass graves in Bosnia Herzegovina, where you find mostly skeletonised remains, but a bit of soft tissue adhering.
"You need to clean these bones up and to preserve the DNA for identification purposes. The old systems included boiling at high temperatures which was extremely destructive to the DNA."
"You need to clean these bones up and to preserve the DNA for identification purposes. The old systems included boiling at high temperatures which was extremely destructive to the DNA."
What these scientists now do is simply heat the remains gently with biological washing powder. The biological enzymes eat away at the flesh, leaving just the bones behind.
What these scientists now do is simply heat the remains gently with biological washing powder. The biological enzymes eat away at the flesh, leaving just the bones behind.
This would certainly make a murder more difficult to investigate but not impossible.
This would certainly make a murder more difficult to investigate but not impossible.
Some people are more likely to deposit their DNA than other people Eleanor GrahamDNA expert
Some people are more likely to deposit their DNA than other people Eleanor GrahamDNA expert
Gunshot and knife wounds may still be visible on the bones, and any blow with a blunt instrument is likely to have shattered or cracked them.
Gunshot and knife wounds may still be visible on the bones, and any blow with a blunt instrument is likely to have shattered or cracked them.
But there is a weapon that wouldn't leave visible evidence behind. It's the one professional assassins favour - poison.
But there is a weapon that wouldn't leave visible evidence behind. It's the one professional assassins favour - poison.
The victim may not even realise what's happened until the murderer is many miles away.
The victim may not even realise what's happened until the murderer is many miles away.
The most recent example is Alexander Litvinenko's poisoning with polonium late last year. It took the investigators weeks to identify the poison, because polonium-210 had never been used in this way before.
The most recent example is Alexander Litvinenko's poisoning with polonium late last year. It took the investigators weeks to identify the poison, because polonium-210 had never been used in this way before.
But what Litvinenko's poisoner may not have realised is that this ingenious poison might also give them away.
But what Litvinenko's poisoner may not have realised is that this ingenious poison might also give them away.
Tiny fibres
Tiny fibres
The alpha radiation given out by polonium-210 can be detected in incredibly small quantities. As the poisoner escaped they were leaving behind a radioactive trail that may yet lead to their capture.
The alpha radiation given out by polonium-210 can be detected in incredibly small quantities. As the poisoner escaped they were leaving behind a radioactive trail that may yet lead to their capture.
This type of trace evidence is the final piece of the perfect murder puzzle. Modern crime scene investigators can spot much more than just fingerprints.
This type of trace evidence is the final piece of the perfect murder puzzle. Modern crime scene investigators can spot much more than just fingerprints.
The CSI team can pick up tiny fibres of clothing, shoeprints from a carpet, and of course DNA.
The CSI team can pick up tiny fibres of clothing, shoeprints from a carpet, and of course DNA.
The world's best detectives are one step ahead
The world's best detectives are one step ahead
And Ms Graham says our DNA may actually make some of us better criminals than others.
And Ms Graham says our DNA may actually make some of us better criminals than others.
"Some people are more likely to deposit their DNA than other people. One person could pick up a bottle of water, put it down, you get a full profile.
"Some people are more likely to deposit their DNA than other people. One person could pick up a bottle of water, put it down, you get a full profile.
"Another one could drink from it and you wouldn't pick up very much. No one knows exactly why this is but there does seem to be a very big difference."
"Another one could drink from it and you wouldn't pick up very much. No one knows exactly why this is but there does seem to be a very big difference."
So if someone sheds less DNA, that would reduce the risk of leaving tell-tale evidence.
So if someone sheds less DNA, that would reduce the risk of leaving tell-tale evidence.
But that's also why the real-life "perfect" murder is likely to fail. It relies too heavily on chance. Every single element must come together perfectly.
But that's also why the real-life "perfect" murder is likely to fail. It relies too heavily on chance. Every single element must come together perfectly.
The forensic scientists need just one mistake and the criminal could be caught.
The forensic scientists need just one mistake and the criminal could be caught.
If someone wants to get away with murder their best hope is to be very, very lucky.
If someone wants to get away with murder their best hope is to be very, very lucky.
Horizon: How to commit the perfect murder is on BBC Two at 2100 BST on Tuesday 8 May
Horizon: How to commit the perfect murder is on BBC Two at 2100 BST on Tuesday 8 May
Add your comments on this story, using the form below.
Add your comments on this story, using the form below.
Of course there may be thousands of perfect murders a year - the point being that if they are perfect murders then no-one will recognise them as such, they will be suicides, accidents or natural deaths. We therefore have no way of knowing quite how good current forensics are.Kasimir, Oxford
Perfect Murder? Elvis Presley.Amara, USA
Perfect murders happen all the time. Every unsolved murder, every missing person, perhaps. The greatest perfect murders have probably already happened because the police defined them suicides or accidents. So the perfect murder is one that one even thinks is a murder. Reno, Southampton, UK
Perfect murders happen all the time. Every unsolved murder, every missing person, perhaps. The greatest perfect murders have probably already happened because the police defined them suicides or accidents. So the perfect murder is one that one even thinks is a murder. Reno, Southampton, UK
If people think that shows like Quincy or CSI show how to commit a perfect murder then they are very much mistaken. Both shows are riddled with scientific errors even an A level student would see through. Regardless of forensic evidence, it's still possible to be convicted of murder even without a body being found.John Airey, Peterborough, UK
If people think that shows like Quincy or CSI show how to commit a perfect murder then they are very much mistaken. Both shows are riddled with scientific errors even an A level student would see through. Regardless of forensic evidence, it's still possible to be convicted of murder even without a body being found.John Airey, Peterborough, UK
I think that there is the "perfect" murder, but probably just by accident. JonBenet Ramsey is one example.Kara Tyson, Mobile, AL USA
I think that there is the "perfect" murder, but probably just by accident. JonBenet Ramsey is one example.Kara Tyson, Mobile, AL USA
This is all very interesting, but is it really responsible journalism? Programs like CSI have already been accused of the "CSI effect" - and they're really just entertainment programs, so the details aren't always realistic or accurate. Even if people don't use your information to get away with crimes, they may think they'll be able to get away with crimes. Therefore, people might commit crimes they'd otherwise have not committed, because of fear of getting caught. There is some information that should be closely guarded - here, the benefit of the information is limited, whilst the potential cost is high.Ankush, Leeds, UK
This is all very interesting, but is it really responsible journalism? Programs like CSI have already been accused of the "CSI effect" - and they're really just entertainment programs, so the details aren't always realistic or accurate. Even if people don't use your information to get away with crimes, they may think they'll be able to get away with crimes. Therefore, people might commit crimes they'd otherwise have not committed, because of fear of getting caught. There is some information that should be closely guarded - here, the benefit of the information is limited, whilst the potential cost is high.Ankush, Leeds, UK
