THC in blood: Mom pleads guilty in daughter, ex-husband deaths

The fiery crash on a Crozet lane last fall left 20-year-old Amber Johnson and her father, Michael Johnson, dead. In court August 29, the driver, Amber's mother, Jessica Marie Lewis, pleaded guilty to two counts of involuntary manslaughter.

Lewis, 37, was driving her Kia Optima November 10, 2011, on narrow Half Branch Road between 67 and 70mph, according to the prosecution, when she slammed into a tree. Neither of her passengers were wearing seatbelts, and a blood test indicated Lewis, who was seriously injured, had smoked marijuana and was using two prescription drugs.

Initially Lewis was charged with two counts of aggravated involuntary manslaughter from driving under the influence, which carries a maximum sentence of 20 years.

Her blood alcohol level showed no alcohol, says Assistant Commonwealth's Attorney Jon Zug, but it did show the presence of tetrahydrocannabinol– the active ingredient in marijuana. Virginia has no legal standards for what constitutes driving under the influence of pot, and one problem for determining such a level is that THC lingers in the blood for weeks after use.

Lewis' THC level was 6 nanograms/milliliter of blood; experts say over 5 ng/mL constitutes driving under the influence, explains Zug.

She also had "borderline therapeutic" levels of anti-anxiety drug Clonazepam, says Zug, and Citalopram, an antidepressant, which was within therapeutic levels.

"There are indications that on the way home, she stopped and smoked marijuana," says Zug. And he said a witness was almost struck head-on by Lewis and estimated her speed at 80mph.

Over and over again, Albemarle police cite speed, seatbelts, and alcohol as primary contributors in fatal crashes. "Obviously, a big factor was [the victims] weren't seatbelted," says Zug. Also were the combination of speed and driving under the influence, he adds.

Involuntary manslaughter carries a maximum of 10 years, and Zug says the Commonwealth has not recommended a sentence, pending victim impact statements.

Lewis' attorney, George Coles, had not responded to a request for comment at press time.

Lewis will be sentenced November 14.