Although Joan Elaine Laidlaw  showed no obvious signs of impairment, prosecutors told jurors her use of marijuana and prescription drugs before driving led to the death of one man and injury to another.

Laidlaw’s trial on charges of manslaughter, aggravated assault, possession of marijuana, possession of drug paraphernalia and driving under the influence started Wednesday in Pima County Superior Court.

She was charged after an October 2012 rollover crash in Vail in which Armando Daniel Hernandez, 18, died and Devin Hermeling was injured.

Deputy Pima County Attorney Ashley Bock argued that before the accident Laidlaw, 42, consumed prescription drugs and smoked marijuana, which contributed to her running a stop sign and crashing her Chevy Blazer at East Old Spanish Trail and South Pistol Hill Road.

Pima County sheriff’s deputies testified they found a bag of marijuana and a glass pipe containing marijuana residue in Laidlaw’s purse. She told police the marijuana was hers and that she smoked daily, but had not smoked since earlier that day. The crash occurred around 9 p.m.

Under questioning by defense attorney Jeff Rogers, Deputy Robert Murray confirmed field sobriety tests he conducted showed no signs of impairment.

Another deputy, Tim Senne, testified that tests he administered to Laidlaw in the hospital did show signs of intoxication, including eyelid tremors and a green film on her tongue indicative of marijuana use.

Tests also found traces of marijuana and prescription drugs in Laidlaw’s blood.

Rogers argued drugs did not play a role in the crash. Rather, he said Hermeling and Hernandez had caused the crash when one discharged a shotgun out the window of the Blazer while Laidlaw drove.

In his opening statements, Rogers said Laidlaw agreed to take Hermeling and Hernandez to the desert to fire shotguns. The two had been friends of her son’s.

After the shotgun outing, Rogers said, Hermeling fired the gun out the window, causing a distraction. Laidlaw then ran a stop sign and drove her Blazer up on a desert embankment, which caused the vehicle to roll over.

The trial continues today in Judge Brenden Griffin’s courtroom.

Contact reporter Patrick McNamara at 573-4241 or On Twitter @pm929.