It's still hard for former CHP Lt. Bob 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 an overwhelming amount of evidence to show that he was under the influence," 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 .08 alcohol level is considered legally impaired, there's no definitive threshhold for "drugged driving."
St. Sen. 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 Tylenol with codeine, xanax, and valium.
"We want to send a clear message," said Correa. Any level of being drugged is dangerous while driving. 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 pot may linger in the body for weeks. They'd rather see an impairment test.
"The problem is they can be driving but the cannabenoids can be staying in their system for 30 days. So they may not be impaired. There may be no problems," said Lanette Davies with Crusaders for Patients Rights.
A 2012 Office of Traffic Safety study found drugged driving is more prevalent in California than drunk driving.