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How DNA Evidence Can Be Faked

written by: •edited by: Paul Arnold•updated: 7/22/2010

DNA fingerprinting is a powerful technology that's been used on thousands of occasions to convict criminals and exonerate the innocent. But, according to a team of researchers in Israel it is now possible to fake DNA fingerprinting evidence. What does this mean for investigations?

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    DNA Fingerprinting

    DNA fingerprinting, invented by Sir Alec Jeffreys is considered a "gold standard" crime fighting technology. It's based on the fact that everyone's genome is unique (apart from identical twins) and has proved to be pretty persuasive in the courtroom. However, like all technology it is not infallible, but could its credibility be undermined by a team of scientists in Israel who have demonstrated that it is possible to manipulate a crime scene by faking DNA evidence?

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    DNA Fingerprinting problems: Fake DNA Fingerprinting

    A team of researchers from an Israeli company called Nucleix has published its work in the journal Forensic Science International: Genetics. They revealed how they took the blood and saliva from one individual and replaced the original DNA with that of a donor's. In the case of blood the scientists centrifuged a blood sample to remove the white blood cells which contain DNA, leaving the red blood cells which do not contain the nucleic acid. Then they added DNA that had been amplified from an individual's hair, and sent it off to a prominent American forensics laboratory that analyzed it as if it was a normal sample. They did not know it was a fake DNA fingerprinting specimen.

    Nucleix are now promoting a test they've designed which they say can spot the difference between a real and a fake DNA sample.

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    Engineering a Crime Scene

    The implications of this paper are pretty startling. In theory a criminal could cover his or her tracks by planting fake DNA evidence at a crime scene, leading to the conviction of an innocent person. However, is this really such a problem? Would the 'master' criminal be well-versed enough in the technology to be able to carry out such an audacious plan? The technology is expensive and complex. And in any case, an innocent person can already be framed by an easier approach. A cup or other object smothered in the fingerprints of an innocent person can be left at a crime scene.
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    It may be one thing to engineer fake DNA evidence, but could it really be left at a crime scene in a convincing way? For example, the semen in a rape victim, or the skin and hair under the fingernails of a murder victim who put up a struggle before dying. What the research has highlighted though is that DNA fingerprinting evidence should not be treated as the be-all and end-all, and its claims must not be exaggerated; it is one tool amongst many. What it does is to place a person at a crime scene. But a crime scene is often littered with the DNA of countless innocent people. Further evidence should be acquired to secure a conviction. So perhaps we should be concerned by the work of the Israeli team, but not unduly worried. There are easier ways to fabricate evidence, and easier defences to mount too.