Los Angeles Police Department Officer Don Inman rubs a swab around the inside of his mouth to demonstrate an on-the-spot drug test being used by law enforcement to deter people from driving under the influence of drugs. (Paresh Dave / Los Angeles Times / December 27, 2013)

An instant drug test will be performed with a swab at some DUI checkpoints during this New Year holiday. A portable, coffee-machine-sized device – the Drager 5000, is capable of analyzing saliva from a suspected DUI driver. It only takes 10 minutes it can detect  cocaine, benzodiazepine (Xanax), methamphetamine, amphetamines, narcotic analgesics, methadone and THC representative of marijuana usage within the past few hours.
A second saliva sample will be stored in a vial, bagged and taken to a private lab to be tested for the specific drug that was detected by the machine.

You don’t need not be drunk to be arrested for a DUI in California.
All a person needs to be is “under the influence” of a substance while driving.

Testing for a DUI is only required after For now the oral swab test is voluntary. But, and this is a big but,
regardless of whether the police are asking you to submit to a breathalyzer, blood, or an oral swab taking a test is not mandatory.
A chemical test to determine if a driver has alcohol or drugs in their system is only required once the person has been arrested on suspicion of driving under the influence. Before that happens, drivers have the right to refuse the test.

A phlebotomist will will also be at checkpoints to take blood samples from suspected DUI drivers.
“Traditionally, our office has focused on drunken driving cases…
if you drink or take drugs, don’t drive,” City Attorney Mike Feuer said at a news conference today. “Our office is aggressively enforcing impaired driving laws and implementing innovative programs to save lives…
Feuer isn’t kidding either. According to him, his office had a 99 percent success rate in prosecuting about 12,000 DUI cases filed in 2013, he said, and they plan to use the additional
evidence from the checkpoint drug testing in their cases.
Aggressive enforcement appears to be working because there were no traffic deaths in LA County this Christmas. CHP reported officers arrested 34 motorists on suspicion of driving under the influence of alcohol or drugs.That is down from last year’s total of 91.
The city attorney’s office filed 577 DUI cases during last year’s two-
week holiday season alone. Injuries and deaths related to alcohol are 86
percent higher around the holidays than during the rest of the year, according
to an analysis by the Automobile Club of Southern California.