DNA WORK FINGERS CANNABIS GROWERS

Forensic scientists in the United States are applying DNA fingerprinting
methods to the cannabis plant.

They say the technique, which is being used to create a database of DNA
profiles of different marijuana plants, will help them to trace the source
of any sample.

"It links everybody together: the user, the distributor, the grower," says
the database's creator, Heather Miller Coyle of the Connecticut State
Forensic Science Laboratory in Meriden.

"That's the real intent of it, to show it's not just one guy with a little
bag of marijuana, but it's a group of people."

A method for spotting the tiniest traces of marijuana, based on detecting
DNA unique to cannabis chloroplasts, has already been developed in Britain.

But the profiling method, based on the same principles as DNA
fingerprinting of people, can distinguish between closely related cannabis
plants.

In a case awaiting trial in Connecticut, prosecutors are planning to use
cannabis DNA profiles to show that two apparently separate cannabis growing
operations were linked.

The two operations, in different parts of the state appeared separate until
analysis of the plants revealed that some had identical DNA fingerprints,
showing that the growers were sharing material.

"From the investigative point of view that was phenomenal," says Timothy
Palmbach, director of scientific services at the laboratory.

The difference between human and plant DNA fingerprinting is that in
people, each fingerprint is unique to one person.

So if a crime scene sample matches a person's profile, there is little
doubt that it came from that individual.

In plants, by contrast, identical clones are easily created by taking
cuttings, a method growers often use to perpetuate potent strains of dope.

So showing two samples have matching DNA profiles does not by itself prove
they come from the same grower, or the same plant.

Mr Palmbach says that growers tended not to give away cuttings of their
best plants, so linking samples was an important lead for investigators.

"What growers have done to get more potent plants has played right into our
hands," he said.

Ms Coyle is establishing a database of DNA profiles from hundreds of
marijuana samples seized in Connecticut.

That database is being extended to include samples from all over the US and
the rest of the world.

Exactly how law enforcement agencies will apply the method remains to be seen.

If a link can be established between a user and a grower or dealer, casual
users might find themselves in deeper trouble than they bargained for.

"If you're buying marijuana from somebody with terrorist ties, it could be
traced back to that person," said Gary Shutler of the Washington State
Patrol's crime laboratory division.

On the other hand, where medical uses of marijuana are legal, the
technology could help characterise strains with the desired medicinal
properties.

Several US states have voted to legalise the medical use of cannabis, a
change being fought by federal authorities.

The technology will not help police investigating the production or sale of
highly processed or synthetic drugs such as cocaine and ecstasy.

Nor does the team think it would work with hashish, which is made from
resin exuded by cannabis plants, as not enough cellular material can be
recovered.

If the cannabis profiling technique does prove to be an effective tool in
investigations and in the courtroom, dealers may switch to selling hashish.

- - NEW SCIENTIST