MARIJUANA DNA TEST FEARS VOICED

LONDON - A new test based on DNA science can tell if people have handled
marijuana, but it is so sensitive that there are fears that innocent people
could be incriminated, the New Scientist said yesterday.

It said researchers had identified DNA sequences within the chloroplast, the
part of the plant cell responsible for photosynthesis, that are specific to
cannabis sativa, the plant name for marijuana, and that are not found in any
other species. The discovery by researchers at the University of Strathclyde
in Glasgow makes it possible to take a swab from someone's hands and test it
for the cannabis DNA sequences.

"This test is as sensitive as you can ever get," Adrian Linacre, one of the
inventors, told New Scientist. "Theoretically, it could pick up the presence
of just one molecule of cannabis DNA."

Because the test multiplies the amount of DNA, it works on minute samples,
unlike existing techniques.

But this acute sensitivity is causing concern.

Chris Evans, of Surescreen Diagnostics, which markets drug-testing kits,
said the test could trap the innocent.

"If you have been driving a second-hand car and a previous owner has been
using cannabis, you could get enough on your hands to test positive," he
told the magazine. Bank notes could also carry trace amounts of the drug.

Linacre said he had calibrated the test so that only relatively large
quantities of DNA gave positive results.

He is developing the test to detect the DNA profiles of different strains of
cannabis, such as those grown in South Africa or Thailand.

"We will be able to use genetic evidence to link different batches of
cannabis and trace them back to their original source," he said.