DNA Evidence Can Be Fabricated, Scientists Show

[Eugen Leitl]

http://www.nytimes.com/2009/08/18/science/18dna.html?_r=1&pagewanted=print

August 18, 2009

DNA Evidence Can Be Fabricated, Scientists Show

By ANDREW POLLACK

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.

bYou can just engineer a crime scene,b said Dan Frumkin, lead author of the
paper, which has been published online by the journal Forensic Science
International: Genetics. bAny biology undergraduate could perform this.b

Dr. Frumkin is a founder of Nucleix, a company based in Tel Aviv that has
developed a test to distinguish real DNA samples from fake ones that it hopes
to sell to forensics laboratories.

The planting of fabricated DNA evidence at a crime scene is only one
implication of the findings. A potential invasion of personal privacy is
another.

Using some of the same techniques, it may be possible to scavenge anyonebs
DNA from a discarded drinking cup or cigarette butt and turn it into a saliva
sample that could be submitted to a genetic testing company that measures
ancestry or the risk of getting various diseases. Celebrities might have to
fear bgenetic paparazzi,b said Gail H. Javitt of the Genetics and Public
Policy Center at Johns Hopkins University.

Tania Simoncelli, science adviser to the American Civil Liberties Union, said
the findings were worrisome.

bDNA is a lot easier to plant at a crime scene than fingerprints,b she said.
bWebre creating a criminal justice system that is increasingly relying on
this technology.b

John M. Butler, leader of the human identity testing project at the National
Institute of Standards and Technology, said he was bimpressed at how well
they were able to fabricate the fake DNA profiles.b However, he added, bI
think your average criminal wouldnbt be able to do something like that.b

The scientists fabricated DNA samples two ways. One required a real, if tiny,
DNA sample, perhaps from a strand of hair or drinking cup. They amplified the
tiny sample into a large quantity of DNA using a standard technique called
whole genome amplification.

Of course, a drinking cup or piece of hair might itself be left at a crime
scene to frame someone, but blood or saliva may be more believable.

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 manbs 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 manbs blood.

The other technique relied on DNA profiles, stored in law enforcement
databases as a series of numbers and letters corresponding to variations at
13 spots in a personbs genome.

>From a pooled sample of many peoplebs DNA, the scientists cloned tiny DNA
snippets representing the common variants at each spot, creating a library of
such snippets. To prepare a DNA sample matching any profile, they just mixed
the proper snippets together. They said that a library of 425 different DNA
snippets would be enough to cover every conceivable profile.

Nucleixbs test to tell if a sample has been fabricated relies on the fact
that amplified DNA b which would be used in either deception b is not
methylated, meaning it lacks certain molecules that are attached to the DNA
at specific points, usually to inactivate genes.