Sacramento, California - Police in three California counties are testing what amounts to a breathalyser for drug users - a device that some authorities and lawmakers say is desperately needed now that voters have legalised recreational marijuana in the state.
When legalisation takes full effect in 2018, California will become the world's largest market for pot, yet it is among the states with legalised marijuana that are struggling to find a reliable test and gauge for marijuana impairment that can stand up in court and lead to convictions.
Law enforcement and academic experts say settling on such a test is complicated because drugs affect everyone differently and there is wide variation in the potency of pot and other drugs and the way they are consumed. As a result, there is no consensus on what level amounts to impairment.
The demonstration of the testing device Wednesday outside the California Capitol involved a Sacramento police officer using a cheek swab to collect saliva from another officer posing as a suspect. The swab was then plugged into a walkie-talkie-sized device that shows within five minutes whether any of six drugs are present in saliva.
California Highway Patrol Sergeant Glen Glaser, who coordinates the patrol's drug recognition expert program, said there were too many variables to rely on a saliva or breath test.
"The science is still developing," he said. "The mere presence of a drug should not make a person feel like they're subject to arrest if they're not impaired."
In addition, prosecutions are more difficult because there is no presumed level of drug intoxication in California, unlike the 0.08 percent blood alcohol level at which drivers are presumed drunk.
Michigan and Vermont recently authorised the tests that are also used in some other states and nations. Suspects in California, however, are currently free to refuse to take the drug tests.
Police mainly rely on field sobriety tests if they suspect a driver is under the influence of alcohol or drugs. While drunken driving tests mainly test physical skills, drugged driving screening also looks for cognitive changes.
For instance, said Glaser, suspects are told to tip back their heads and estimate when 30 seconds have passed; some drugs make time seem to slow down while others produce the sensation that time has accelerated.
Alere Toxicology product manager Fred Delfino said the company's device, demonstrated on Wednesday, has an accuracy rate of 95 percent, enough to identify which drivers should be required to provide blood samples to show the actual level of intoxication.
Lauren Michaels, marijuana and drunken driving policy expert for the California Police Chiefs Association, said more California police departments were using the saliva tests after a Kern County judge in 2016 accepted the results as admissible evidence in a drugged driving case.
The CHP and other agencies are cooperating with the Centre for Medicinal Cannabis Research at the University of California, San Diego, as part of a two-year, $1.8 million (R24 million) study to analyse and try to improve tests used by human drug-recognition experts.
Thomas Marcotte, the study's chief investigator and co-director of the research centre, said researchers were also trying to learn if there was a particular level of marijuana intoxication that impaired driving.