How DNA Evidence Can Be Falsified
A new test distinguishes between real and fake genetic evidence.
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.
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… 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.
