How DNA Evidence Can Be Falsified

An Israeli company, called Nucleix, has shown that it’s possible to fake DNA evidence at a crime scene, a possibility that has been cited as a concern for those who make their genome sequence public. Nucleix, based in Tel Aviv, has also developed a test that can distinguish between real and fake DNA evidence, i.e. DNA that has been shed from a person, and synthesized DNA that has replicated from a small DNA sample or generated anew from an individual’s genome sequence.

According to a report in The New York Times,

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.

… The authors of the paper took blood from a woman and centrifuged it to remove the white cells, which contain DNA. To the remaining red cells they added DNA that had been amplified from a man’s hair.

Since red cells do not contain DNA, all of the genetic material in the blood sample was from the man. The authors sent it to a leading American forensics laboratory, which analyzed it as if it were a normal sample of a man’s blood.

The new test can distinguish between real and fake DNA evidence by anaylzing patterns of DNA methylation, a chemical modification that alters the shape of DNA molecules. According to a press release from the company,

…in vivo-generated DNA contains loci that are completely and consistently methylated and other loci that are unmethylated, differing from in vitro-synthesized DNA, which is completely unmethylated. Nucleix’s novel proprietary assay can identify and differentiate between real and all potential types of fake DNA through methylation analysis of a set of genomic loci. Results of the company’s research demonstrated both the current risk in sample integrity and the success of Nucleix’s new approach to DNA source verification.