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EVERY time the police take a saliva or blood sample for DNA fingerprinting
they are unknowingly collecting sensitive information about the health of the
suspects they are testing.

A British team has discovered that the DNA fingerprints used by police across
the world can reveal a person’s susceptibility to type I diabetes. The finding
strikes at the heart of one of the principles of DNA forensic
testing—namely, that tests should identify people but reveal nothing
significant about their genetic make-up or health. That way, DNA profiles can be
stored on police computers without infringing anyone’s medical privacy.

The fingerprints held by police are based on specific regions of a person’s
DNA, known as “markers”
(see “Could it be you”).
These markers are not supposed to carry information about a person’s genes.

Yet John Stead of the University of Leicester and his colleagues found that
one of the 10—a marker called THO1—does carry such information.
While the marker is not thought to influence health directly, it is located
close to the gene for insulin. That means it can reveal whether someone has
“risky” or “protective” versions of the gene, and thus has a slightly greater or
lesser chance of getting diabetes. But you cannot tell for sure if someone will
get diabetes.

“This marker is weakly linked to a shift in your predisposition to diabetes
and the police should not be collecting that type of information,” says team
member Alec Jeffreys of the University of Leicester, who invented DNA
fingerprinting. He thinks it is possible that other forensic markers could also
be linked to medical conditions or traits.