by Andrew Pollack
August 17, 2009
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.
“You can just engineer a crime
scene,” said Dan Frumkin, lead author of the paper, which has
been published online by the journal Forensic Science
International: Genetics. “Any biology undergraduate could
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
anyone’s 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
Celebrities might have to fear “genetic
paparazzi,” 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.
“DNA is a lot easier to plant at a
crime scene than fingerprints,” she said. “We’re creating a
criminal justice system that is increasingly relying on this
John M. Butler, leader of the
human identity testing project at the National Institute of
Standards and Technology, said he was,
“impressed at how well they were
able to fabricate the fake DNA profiles.”
However, he added,
“I think your average criminal
wouldn’t be able to do something like that.”
The scientists fabricated DNA samples
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
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 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 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 person’s genome.
From a pooled sample of many people’s 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
Nucleix’s test to tell if a sample has
been fabricated relies on the fact that amplified DNA - which would
be used in either deception - is not methylated, meaning it
lacks certain molecules that are attached to the DNA at specific
points, usually to inactivate genes.