Charges Against Man Accused Of Killing Trooper Highlight Lack Of Marijuana Legal Limits For Drivers

WORCESTER (CBS) -- Prosecutors say when David Njuguna crashed his car into the back of State Police Trooper Thomas Clardy's cruiser, the Webster, Mass. man was high on marijuana.

The Worcester DA says a partially burned marijuana joint and three other medical marijuana joints were found in the car. They also say the defendant had levels of THC in his blood. This evidence is the basis of charging Njuguna with motor vehicle homicide while operating under the influence of drugs.

A legal expert told WBZ-TV it will be hard to get a conviction on that. The reason? Unlike drunk driving, there is no legal limit for pot.

Attorney Peter Elikann said that while police can use a breathalyzer for alcohol, there's no such tool for marijuana.

"Marijuana can stay in your system so many weeks," said Elikann. "At this point, they don't really have a way to prove it and people don't have to take a blood test at all."

Elikann says even thought a burned joint was found in Njuguna's car, they cant prove he smoked it.

"The fact that they may not be able to prove he operated under the influence doesn't mean he walks away scot-free," Elikann said. "They [prosecutors] still have have stronger manslaughter case."

Governor Charlie Baker was asked about the subject Thursday and said the idea of looking into establishing a legal threshold for pot is a good one.