DNA evidence needs to be handled with care | South China Morning Post
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  • Mar 3, 2015
  • Updated: 8:00am

DNA evidence needs to be handled with care

PUBLISHED : Monday, 24 August, 2009, 12:00am
UPDATED : Monday, 24 August, 2009, 12:00am

A group of Israeli scientists has recently caused alarm by showing how DNA evidence can be manufactured - showing how it is theoretically possible, using sophisticated techniques in molecular biology and genetic profiling, to fabricate DNA evidence to implicate an innocent person or violate his or her privacy. The implications are disturbing for many people because DNA evidence has long been considered the gold standard of proof in criminal cases.

Perhaps one should worry about the reliability of DNA evidence, but not only because of this latest development.

In one technique, the scientists extract a DNA sample from person A, produce a large quantity of it, and then mix it with a DNA-free blood sample taken from person B. In another method, the researchers clone tiny DNA snippets and recombine them to match any DNA fingerprint data on record. The Israeli scientists said any well-trained undergraduate biology student could master the techniques. Their research is good material for thrillers, but it is not clear how foolproof these techniques are from detection. In any case, in the real world, it is unlikely too many criminals will go to such great lengths to recreate a crime scene.

The real worry is not that such new methods will undermine otherwise foolproof evidence, but more the great weight we currently put on such information. Properly conducted, DNA evidence can provide a high level of proof and accuracy. But this is not always the case. Contamination, sloppy procedures, badly trained or corrupt personnel, improper storage and collection, and something as simple as mislabelling a DNA sample - all these have been known to have compromised criminal investigations in jurisdictions around the world. And while standard DNA fingerprinting is highly reliable, another DNA technique known as low copy number (LCN),which amplifies minute genetic material until there is enough to be analysed, does not have the same accuracy level. DNA evidence is the most reliable method in the arsenal of forensic science, but it still needs wise handling.


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