A Welsh assembly member who called for his colleagues to volunteer to try out a new drug detection machine has tested "positive" for cannabis himself.
Politicians' hands could have picked up drug traces from handling cash or using a door
Swabs taken from Conservative AM William Graham's hands at the Welsh assembly building revealed traces of the drug, probably from a door handle.
He had arranged for police to come in to demonstrate the hi-tech machine.
Social Justice Minister Edwina Hart's hands were similarly cross-contaminated also bringing a positive test.
Mr Graham, a long time campaigner on substance abuse issues, said: "I can't think where I could have got it from".
He had arranged with Gwent Police, who had recently bought the first Ion Track drug detection system in Wales at a cost of £40,000, to demonstrate it to assembly members in Cardiff Bay.
The machine can detect traces of drugs or explosives several days after a person has come into contact with them, even if they have washed their hands.
The machine can trace minute traces of drugs
A swab paper is wiped over a person's hands and then placed into the machine which then analyses it for drugs including cocaine, heroin, ecstasy and cannabis.
The resulting reading indicates how many drugs are present in the sample and at what levels.
It is so sensitive it can detect the equivalent in drugs of a grain of salt in an Olympic-sized swimming pool.
A similar test of fellow AM Ms Hart showed that although she had not been using drugs, her hands had been cross contaminated with traces of the substance, from door handles, money or other public areas.
"You could pick it up from anywhere couldn't you?" she said.
The machine is used by Gwent Police to test people queuing for a night club, and to detect traces of drugs in a house where the actual substances had already been removed.
A spokesman for Gwent Police said: "It must be borne in mind that anyone taking the test can test positive as a result of cross contamination."
Other AMs lined up to have swabs of their hands tested by the machine with Jonathan Morgan and Owen Jon Thomas both coming up "clean" on the machine.
Nick Bourne, leader of the Welsh Conservatives, also got a clear result.
"May I pay tribute to the Ion Track system, despite the fact that both the minister and William Graham tested positive on it - I was relieved that I didn't - but it is an excellent system nevertheless," he said.
Ms Hart responded: "It can come out of cash, out of a cashpoint, a beer mat, or anything else. It is a very sophisticated system that can pick up anything if you have been in contact with someone's jacket or anything."
Divisional Crime Prevention Officer Pc Simon James said that while the results could not be used as evidence, they can indicate to officers that a person should be searched or questioned.
Mr Graham, who represents South Wales East, said: "Anything that deters people from taking drugs is a good thing. If people know this thing exists then they will know that they might get caught".