When Benjamin Cope drove his SUV into a Mt. Lebanon woman and the stroller she was pushing, killing her on June 28, 2010, he had a low level of the active ingredient in marijuana in his blood stream.
Jennifer Janssen, the assistant chief toxicologist for the Allegheny County Medical Examiner's office, told a jury Tuesday in Mr. Cope's trial that the level in his blood, along with reports from police officers at the scene that he failed a variety of field sobriety tests, allowed her to conclude that the young man was not capable of safe driving at the time of the crash.
"In determining impairment, we look at the totality of the circumstances," she said.
Generally, the active ingredient in marijuana will peak in the bloodstream nine to 10 minutes after the drug is smoked, Ms. Janssen said. It then decreases quickly after that, until two to three hours later, when it becomes undetectable in the blood.
"The effects will last three to five hours," she said. "However, there are residual effects that last up to 24 hours."
Those residual effects include problems with "complex divided attention skills," such as driving. Other effects can include impaired time, space or depth perceptions, as well as an inability to concentrate or "maintain vigilance."
But in cross-examination, defense attorney Bruce Beemer rattled off a list of his client's physiological responses at the scene that day -- his pulse was not increased, his eyes were not red, his blood pressure was steady and his reaction to light was appropriate.
Ms. Janssen acknowledged those reactions but said they did not change her opinion.
She told the jury that based on two different ingestion models, Mr. Cope likely smoked marijuana between 8 a.m. and the time of the crash.
However, Mr. Beemer asked if that estimate was valid if his client smoked marijuana every day.
Ms. Janssen said it was not and that she could not pinpoint a specific time period in such an instance.
"It is possible that someone who is a daily user would have a baseline level in their blood," Ms. Janssen said.
First Published: September 21, 2011, 2:30 p.m.
