"Perhaps the alcohol laws are effective, but actually not the drugged-driving laws," said former California Highway Patrol Lieutenant Bob McGrory.
It's still hard for McGrory to talk about the death of his son, Justin, who was also a highway patrolman. The 28-year-old was killed in 2010 when Rafael Garcia swerved into him during a traffic stop. McGrory says Garcia had marijuana in his system, but the case ended in a hung jury.
"The jury was unable to come to a conclusion whether he was under the influence, even after having overwhelming amount of evidence," said McGrory.
The McGrory tragedy highlights how difficult it is to prosecute cases in California involving drivers under the influence of drugs.
Unlike sobriety tests where a 0.08 blood-alcohol level is considered legally impaired, there's no definitive threshold for "drugged driving."
State Senator Lou Correa (D-Santa Ana) has introduced a bill that makes it illegal to be behind the wheel with any detectable amounts of Schedule 1 through 4 drugs unless you have a prescription.
According to the U.S. Department of Justice, that includes Xanax, Valium and Tylenol with codeine.
"Any level of being drugged is dangerous in driving," said Correa. "So the level should be zero. Zero tolerance."
A prescription, though, doesn't give drivers a pass. An officer can still pull over anyone whose driving appears impaired.
Not everyone agrees with the proposal. Opponents say the measure is too tough on those who legally use medical marijuana and those who use over-the-counter cold medicines.
They claim ingredients in Claritin and Dayquil could cause someone to test positive for drugs. And cannabis may linger in the body for weeks.
Opponents would rather see an impairment test.
"The problem is they can be driving but the cannabinoids can be staying in their system for 30 days. So they may not be impaired. There may be no problems," said Lanette Davies, director of Crusaders for Patients Rights, a Christian-based patient's right organization for cannabis patients.
A 2012 Office of Traffic Safety study found drugged driving is more prevalent in California than drunk driving.