Israeli scientists demonstrate how blood samples could be used to incriminate or exonerate suspects.
By JUDY SIEGEL-ITZKOVICHDNA generic 248.88(photo credit: Courtesy)
The possibility that clever criminals could fake DNA from blood and saliva samples to incriminate or exonerate suspects has been demonstrated by scientists at the Weizmann Institute of Science in Rehovot and the Israel Police's Identification and Forensic Science Division.
Dr. Dan Frumkin, Dr. Adam Wasserstrom, Ariane Davidson and Arnon Grafit just published their eyebrow-raising article in FSI Genetics (Forensic Science International, part of Elsevier's prestigious family of journals, Genetics).
The news that the "gold standard" of proof in criminal cases could be fabricated has aroused much interest after being published worldwide in The New York Times and broadcast on CBS TV.
According to the journal article, Frumkin and colleagues were able to fabricate biological samples containing DNA and - using their access to a DNA profile in a genetic database - build a DNA sample to correspond to that unique profile even without receiving any biological material from the person to whom the profile belongs.
The authors claimed that one would not need to be a forensic expert to do this, but only to have studied a few years of college-level biology.
As a result of this technique, lawyers and courts could conceivably be unable to pin rape, murder or other crimes on a suspect whose DNA samples were left at the crime scene or on victims.
However, DNA sample testing need not be eliminated as a method of identifying criminals, the Israeli researchers wrote. They developed a test to authenticate results by distinguishing between natural and artificial DNA, based on "methylation analysis" of certain points in natural DNA, and successfully used it on natural and artificial samples of blood, saliva and touched surfaces.
They concluded that it was necessary for crimebusters to adopt an authentication assay for biological samples at crime scenes or on victims to maintain the high credibility of DNA evidence in the judicial system.
Prof. Ephrat Levy-Lahad, head of the medical genetics institute at Jerusalem's Shaare Zedek Medical Center, told The Jerusalem Post on Tuesday night that criminals with such intentions could do this with existing technology and some knowledge of genetics.
"They would need access to devices that perform polymerase chain reactions (PCR) to magnify DNA. Since the development of the whole genome amplification (WGA) technique several years ago instead of examining just one specific section of an individual's genome, this is possible, but I haven't heard of PCR crimes being committed with it," said Levy-Lahad.
"Maybe nobody bothered to do so, but the principle is clear. WGA produces a large amount of DNA that represents a person's whole genome, and this technique is constantly getting cheaper."
Frumkin, who was not available for comment, wrote in the journal article that "over the past 20 years, DNA analysis has revolutionized forensic science and has become a dominant tool in law enforcement. Today, DNA evidence is key to the conviction or exoneration of suspects of various types of crime, from theft to rape and murder. However, the disturbing possibility that DNA evidence can be faked has been overlooked."
The authors wrote that "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."
They added that when both artificial and natural samples were genotyped, full profiles with no errors were created.
"This artificial DNA can then be applied to surfaces of objects or incorporated into genuine human tissues and planted in crime scenes," they wrote. "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."
Prof. Yosef Almog, a Hebrew University applied chemistry expert and former Identification and Forensic Science Division director, told the Post that the ability to cheat was "certainly a nuisance. To fabricate DNA in the described way, the forgers will need a good knowledge of forensic DNA technology, as well as access to specific reagents and instrumentation.
"However, fabrication can be achieved also by simpler means such as 'planting' somebody else's blood, saliva, hairs or even semen at the scene. DNA analysis of the exhibits will obviously lead to the wrong person."•
