Israeli Scientists Show That DNA Evidence Can Be Faked
Tuesday, August 18, 2009 at 11:07 PM EDT
Anyone who watches CSI, NCIS, or any of the many other crime shows on (US) network television will be familiar with the concept of DNA evidence. Not just on TV, but in real criminal investigations, DNA evidence has been regarded as the â€œgold standardâ€. In some cases it has irrefutably placed a suspect at a crime scene; in other cases, the use of DNA evidence and analysis that was not previously available has demonstrated the innocence of someone wrongly convicted of a crime. Basically, a DNA test starts with a small sample of genetic material; that sample is then â€œgrownâ€ in size by carrying out a procedure through which the DNA is replicated. This generates enough DNA that its genetic code can be sequenced. A comparison is then made among several regions of so-called â€œjunkâ€ DNA. These sequences are not believed to have any genetic significance in humans, and thus should be subject to random mutations; if long enough sequences are compared, the likelihood of a match by chance is very small.
That is the theory, at least. The New York Times has a report that a group of Israeli scientists has demonstrated the feasibility of producing â€œcounterfeitâ€ DNA, in a test tube, mimicking that of a selected person, such that currently used tests cannot distinguish between the counterfeit and the real thing. In a paper [abstract] to be published in the journal FSI Genetics, the authors describe two experiments in which they made fake DNA. In the first, they start with an actual biological sample containing a personâ€™s DNA; in the second, they use a previously determined DNA sequence from a data base:
They found that these sample would match their target when subjected to a routine DNA analysis, without any noticable anomalies. Assuming their result holds up, this means that faking DNA evidence at a crime scene, or for other purposes, could be done fairly easily. From the abstract:
These techniques do require some specialized knowledge and equipment, but probably nothing that could not be found in a typical university laboratory.
The researchers, three of whom are associated with the Israeli company Nucleix Ltd, also claim to have developed a test that can distinguish between artificially produced DNA and natural DNA. The test relies on the observation that, in natural DNA, some geneetic loci are methylated, whereas artificial DNA there is no methylation.
It will be interesting to see if there is any follow-on to this research. But it once again suggests that jumping to the conclusion that any forensic technique works infallibly is a Real Bad Idea.
This article originally appeared on Rich's Random Walks.