“Authentication of forensic DNA samples” is a paper released on the last Forensic Science International: Genetics issue by a group of Israeli researchers. Authors claim to have found a method to fabricate artificial biological samples (and the way to tell the differences from the original one) and wish that their finding will become a standard in forensic procedures to maintaini “the high credibility of DNA evidence in the judiciary system.”
Does this method really affect criminal investigations and trials?
“We still are in the “bad cop” (or evidence tamperer) field who planted faked biological samples on the crime scene” – says Andrea Cocito, researcher at IFOM, Milan (IT.) In fact, the “fabricated-genetic-evidence defense” has been proven viable in the ? OJ Simpson case tried between 1994 and 1995 in Los Angeles, USA. Mr. Simpson’s lawyers were able to raise the suspicion that the results of the analysys on the biological samples coming from the crime scene – aiming at Mr. Simpson as “owner” of the DNA – weren’t reliable enough because of the police handling lack of care. “If” – Cocito argues – “a biological sample has ? really been found on the crime scene, if the sample isn’t planted and if it’s not been degraded, then I might analyze both samples (the crime scene one and the one belonging to the defendant) to see if I get a match. In these case, there couldn’t be reasonable doubts on the results.” Thus, matching the defendant biosample collected in a controlled environment with the sample found on the crime scene it is possible to tell the probability of a reciprocal match.
The actual problem, then, is not the intrinsic scientific reliability of a genetic analysis-produced evidence. The problem is the strength of the chain of custody (i.e. the possibility of tracking all the intermediary steps, from the crime scene to the Court.) It is evident that if during the journey some part of it is not verifiable, a possibility comes to arise a legitimate doubt that what came in Court might not be what has been found on the crime scene.
On this issue, Italian law n. 85/2009 that creates a local National DNA Database is very lazy. There is neither any explicit duty of guaranteing the chain of custody, nor a provision that prevent the use in Court of wrongly-handled biological samples.
This is the translation of an article I’ve written for Nova-IlSole24Ore. The Italian version is available here.