Tuesday, August 18, 2009
Today's New York Times has an article about fabricating DNA evidence in a laboratory. Unlike naturally-occurring DNA that could merely be planted at a crime scene, fabricated DNA would not require access to an original, physical specimen of a particular person's DNA, so long as one had access to his DNA database profile. An excerpt from the NYT:
Scientists in Israel have demonstrated that it is possible to fabricate DNA evidence, undermining the credibility of what has been considered the gold standard of proof in criminal cases.The scientists fabricated blood and saliva samples containing DNA from a person other than the donor of the blood and saliva. They also showed that if they had access to a DNA profile in a database, they could construct a sample of DNA to match that profile without obtaining any tissue from that person.
“You can just engineer a crime scene,” said Dan Frumkin, lead author of the paper, which has been published online by the journal Forensic Science International: Genetics. “Any biology undergraduate could perform this.”
In the abstract of their paper, the researchers state:
It turns out that standard molecular biology techniques such as PCR, molecular cloning, and recently developed whole genome amplification (WGA), enable anyone with basic equipment and know-how to produce practically unlimited amounts of in vitro synthesized (artificial) DNA with any desired genetic profile. This artificial DNA can then be applied to surfaces of objects or incorporated into genuine human tissues and planted in crime scenes. Here we show that the current forensic procedure fails to distinguish between such samples of blood, saliva, and touched surfaces with artificial DNA, and corresponding samples with in vivo generated (natural) DNA.
Quite coincidentally, we can be sure, most of the authors of the paper are affiliated with a company called "Nucleix" that markets a test to distinguish natural from artificially-created DNA. They sell a test that can be used as a countermeasure to detect fabricated samples:
Nucleix’s test to tell if a sample has been fabricated relies on the fact that amplified DNA — which would be used in either deception — is not methylated, meaning it lacks certain molecules that are attached to the DNA at specific points, usually to inactivate genes.
I suspect that most geneticists would not at all be surprised about the possibility that DNA crime scene evidence could be fabricated. It would be interesting to hear more independent opinions about just how easy or difficult the fabrication process would be, aside from the true, but unsurprising, comment by John Butler, “I think your average criminal wouldn’t be able to do something like that.” Still, the article already gives us at least some reason to question the DNA found at crime scenes where people with the know-how and resources to fabricate DNA may be involved.
The New York Times article does not reveal whether there are countermeasures to the countermeasures. Perhaps DNA can (or someday could) be artificially methylated in a way that makes it difficult to distinguish natural from artificially-created DNA. If so, Nucleix's current test would likely prove insufficient, and some more refined test would be necessary. The more difficult we can make it to fabricate a sample that seems natural, the more we can trust the evidence that passes our tests.