This year, California could join a parade of states marching toward legalization of adult recreational marijuana use. But here, as in Colorado, Washington and other states that have already taken the leap, many anti-pot cops and a pro-pot advocates agree: No one yet has devised a practical and reliable field test to determine when a driver is under the influence of marijuana.

State Sen. Bob Huff, who represents parts of Orange, Los Angeles and San Bernardino counties, is proposing legislation that would authorize use of saliva swab tests, which combined with portable instruments can detect the presence of pot and other drugs.

Backers of the swab test — now widely used by law enforcement in the United Kingdom and by companies stateside to screen potential employees for drug use — say it offers a quick and cheap way to help establish probable cause to further test for drugs that can impair drivers.

But critics say the roadside device is still too experimental and unreliable to be put into wide use. Also, authorities say early tests show it’s least effective on the two types of drugs they most frequently encounter: marijuana and prescription medicines.

Fullerton police tested the technology in recent years but never used the results in a DUI prosecution. At this point, it doesn’t appear any local public safety agency is using the oral swabs in the field.

But with drugged driving crashes up and Californians weighing legalization of recreational pot, Huff and others say a new tool is needed to keep roads safe.

“In 2013, in 32 percent of all auto fatalities in California people tested positive for driving under the influence of either legal of illegal drugs,” Huff said. “It seemed like the right time to do this.”

How does it work?

Huff’s legislation, Senate Bill 1492, wouldn’t mandate the use of oral swab tests. But it would set standards for law enforcement agencies interested in using the devices, the senator said, and free up federal funding to help buy the equipment.

As with all DUI cases, the law states officers would first need reasonable cause to believe someone is driving under the influence, such as erratic driving or a crash.

If the driver fails a field sobriety test, the officer would give them the option of taking a saliva test — akin to the breath tests offered to drivers suspected of being under the influence of alcohol.

To participate, a driver would briefly hold a small wand in his or her mouth. Officers then use a hand-held device about the size of half a loaf of bread to read the results. In five to 10 minutes, the device changes color to indicate traces of drugs including cocaine, amphetamines, marijuana and opiates.

If the driver passes the test, Huff said he or she would typically be free to go. If they fail the test or refuse to take it, they’d be taken to the station for a blood test to measure the level and type of substances in their system.

Testing the tech

The Orange County District Attorney’s Office partnered with Fullerton police and the county crime lab to test saliva swab tests from November 2013 to April 2014. Similar pilot projects took place through a federal grant in Los Angeles, Bakersfield and Sacramento.

For suspects who volunteered to take the test, Susan Price, the O.C. district attorney’s assistant head of courts, said authorities pledged only to use the samples to further scientific research and not for evidence.

Tests found that the device is most effective in testing for drugs such as cocaine and amphetamines, Price said. When it came to marijuana and prescription drugs, she said, there were several false positives and false negatives.

One of the state’s first examples of saliva swabs being used as evidence in court occurred in December in Bakersfield, where the kits had been field tested. Defense attorney Jared Thompson said the results actually helped his client fight more serious charges in a vehicular manslaughter case.

The swab test didn’t indicate the presence of pot, Thompson said. However, a blood test showed his client had alcohol, methamphetamine and marijuana in his system when he crashed his car, killing another motorist. The contradictory results were enough to raise doubts in jurors’ minds, he said. His client was convicted of vehicular manslaughter while intoxicated, he said, but acquitted of an additional gross negligence charge.

The accuracy of swab kits tested in Bakersfield and Los Angeles was 98.9 percent, said Brian Shaffer, a spokesman for Dräger, the German firm that manufactures the tests.

One challenge with drug testing is there’s no clear scientific standard to determine when a driver is illegally impaired. Price said that’s because so many factors affect how the body metabolizes drugs, including the person’s tolerance, the potency and the method of ingestion.

Marijuana in particular stays in the system for a long time, points out Kandice Hawes, executive director of the Orange County chapter of NORML, a nonprofit that advocates for legalization. That makes it harder to determine whether a driver is legally impaired or used the drug the night before, say for medicinal reasons, she said.

Shaffer insisted Dräger’s kits detect the psychoactive or mind-altering chemicals in drugs, which he said only would be present in people who’d recently ingested them.

Researchers and regulators play catch up

Research to establish a state standard for marijuana impairment is just gearing up. Under the Medical Marijuana Regulation and Safety Act, California will partner with UC San Diego’s Center for Medical Cannabis Research Center to study how pot impacts motor skills.

Researchers hope to correlate performance on a driving simulator with ingestion of marijuana, including the effects of pot with different potencies, according to Dr. Igor Grant, who chairs the university’s Department of Psychiatry. The study will assess how lab measurements might be adapted for use in the field and how different types of field tests, including swab kits, compare.

The center hopes to have state approval and begin its research in the fall.

Another Assembly bill introduced in February would establish a legal driving limit for marijuana users at 5 nanograms per milliliter of blood – the same as limits imposed in Colorado and Washington. To get a conviction, though, AB 2740, introduced by Assemblymen Tom Lackey, R-Palmdale, and Evan Low, D-Silicon Valley, would also require corroborating evidence of impairment, such as failing a field sobriety test or unsafe driving.

Law enforcement hesitant

Officials at several local police departments said they hadn’t heard of the saliva swab tests. Others said they’re waiting to see what the researchers find and courts allow.

“If the technology changes and the law changes with it to allow for another method of testing, we will look at the new technology to see if it is reliable and cost-effective for us to implement,” said Sgt. Daron Wyatt with the Anaheim Police Department. “However, for now, we will be staying with blood and breath.”

The Huntington Beach Police Department’s traffic division reviewed the tests about a year ago, according to Officer Jennifer Marlatt. The agency opted not to move forward, after questions were raised about the cost effectiveness of adding another investigative tool.

Huff’s bill has sparked concern from groups like NORML, who think it’s too early to implement the roadside kits statewide.

“We do not feel there is enough scientific evidence proving the tests’ validity,” Hawes said.

Shaffer points out his firm’s Dräger DrugTest 5000 has been used for eight years, with roughly 1 million tests performed in Europe, Australia and the United States.

“If it was 100 years old, it would be too new for the marijuana community,” Huff said.

Despite the limitations of swab testing, Price said she’s encouraged by the attention that’s being paid to reducing drugged driving.

“The technology of the oral device that’s being tested is very promising,” Price said, “and it’s something we look forward to having as an additional tool in the field.”