A Wisconsin law that targets drugged driving is being criticized by lawyers and defendants as being unfair and too rigidly applied, the Wisconsin State Journal reported Nov. 2.

The law states that a blood test revealing any detectable amount of a drug that could cause impairment is enough to prove a driver guilty of driving under the influence. Police don't have to prove that a driver was impaired by drugs. If a death is involved, the driver can be charged with homicide by drugged driving.

Thirty-three people in Wisconsin have been charged with homicide by drugged driving, with five convictions on that charge and prison time for most of the others for some other form of vehicular homicide.

John Hyland, a lawyer representing a defendant accused of drugged driving, said that the law is "extremely unfair as it creates a strict-liability offense, something which is exceptionally rare in our criminal code." Some drugs can trigger a positive drug-test result even weeks after use, experts say.

"The difference between having a detectable amount of controlled substance in your blood versus having a scientifically demonstrable impairment because of the drug is the difference between a rational law and a law based on wanting to punish people based on using drugs any way we possibly can," said Peter Steinberg, a Madison attorney.

Setting standard blood concentrations for intoxication with most drugs would be difficult, said Laura Liddicoat, director of the forensic toxicology program at the Wisconsin State Laboratory of Hygiene.

In 2005 the law was challenged as unconstitutional but was upheld by the state appeals court.