The tests have already been used at DUI checkpoints and some jails, but now they'll be rolled out at regular, everyday traffic stops to test for seven drugs, marijuana chief among them.
Criminal defense attorney Mark A. Gallagher has been working L.A. County Superior Courts for nearly 15 years. He gave us a few tips on what to do if you're faced with the swab:
Gallagher says he understands why cops are making this move. "So many people are driving around high" these days, he says.
That was the idea when City Attorney Mike Feuer announced the 2014 swab expansion recently:
... Medical marijuana dispensaries are prevalent here in Los Angeles ... There are those who are driving under the influence of medical marijuana.
But you have rights, too. When an officer asks you to take the swab, you can say no. For now. The cops may try to suggest otherwise, but that's more strategy on their part than a legal right
"Cops can do whatever they want if you consent -- draw your blood, search your car, come to your house," Gallagher says. And beware the officer who tries to talk you into giving that consent against your best interest: "Cops are always going to try to use their badge and stature to guide you toward consenting."
But unless you're under arrest, California court precedent says that police must have a warrant to take blood for purposes of determining if there are drugs in your system. For now it will be assumed the same applies to the swab.
The City Attorney's office acknowledges that drivers have the right to say no.
"We're still pretty protected there," Gallagher says.
However, the lawyer says the legislature will likely come up with a law to give police some leverage -- an administrative penalty of the type you face if you refuse a blood test for allegedly driving drunk.
If an officer believes you've been drinking and driving -- if they have "probable cause" (the smell of booze, slurred speech, etc.) -- they can request that you take a blood test. If you refuse, you face an automatic, one-year suspension of your drivers license.
Even if you refuse the test and opt for the suspension, you can still face a criminal DUI case, though prosecutors might be lacking the kind of evidence they want.
And for now, if you refuse that swab, there isn't even that administrative penalty. You have every right to say no -- which is exactly what this lawyer recommends you do.
"Definitely refuse," Gallagher says. "It makes it a tougher case to prove."
The threshold for what constitutes stoned driving hasn't been established. There's no statewide standard for how much THC you can have in your blood and still be considered okay to drive.
Medical marijuana activists have expressed concern that medicinal users will be prosecuted for having toked up days before they were pulled over. THC, after all, can stay in the bloodstream for weeks.
"The whisper number" prosecutors are talking about for weed DUI, Gallagher says, "is 5 nanograms of THC per milliliter."
Alcohol DUI cases are hard to defend, he says, namely because it comes down to public perception. But, for now, you have a chance if you're arrested for stoned driving:
Who's going to be pro drinking and driving? It's a tough sell. With marijuana there are good scientific arguments about how much, when and how it affects your ability to drive. There are scientists out there who can testify that its safe to drive on some marijuana. You won't get any to say that about alcohol.