RCMP in Mission are blaming cannabis for a crash on the Lougheed Highway that left a man in his 60s dead.

“It is believed that marijuana use was a contributing factor to this incident,” read a statement from authorities. “The driver of the Dodge truck, a 25 year old Abbotsford resident, was arrested.  The investigation is continuing and a charge of impaired driving causing death will be recommended by police.”

While impaired driving tests are inconsistent across the country, a Canadian Centre on Substance Abuse study said the amount of substance-positive drivers rose from around 30 per cent in 2000 to just under 37 per cent in 2008.

Statistics Canada numbers for those charged with drug-impaired driving rose from 183 in 2008 to 1,159 in 2013.

According to a 2011 study of B.C. drivers published in the B.C. Medical Journal, cannabis use is “particularly high,” in the western province, finding 4.6 per cent of drivers in Vancouver and Vancouver Island tested positive for cannabis.

Canadian Centre on Substance Abuse senior research associate Doug Beirness said testing drivers for cannabis is more difficult than alcohol, which can be detected easily with a driver’s breath.

“You have to do the research to be able to determine what the most appropriate limit is for each and every substance that could possibly impair driving,” said Beirness. “That’s a daunting task. It took us 50 years to come up with the level of 80 [milligrams of alcohol in 100 millilitres of blood] for alcohol. We don’t have the time to do that.”

Blood and urine tests can detect levels of cannabis in a driver’s system, but are unable to tell when it was consumed – sometimes staying in a user’s system for up to weeks.

Without standardized testing methods and restricted levels, cannabis impairment is difficult to prosecute.

A 2011 verdict from an Ontario judge on a suspect police had arrested for driving under suspicion of cannabis impairment dismissed the charge as “there is an evidentiary problem with drug cases.”

“There is no standard and no norm as there is with blood alcohol consumption. The court is left in a doubt as to the quantity of THC,” said Judge Bishop.