THORNTON, Colo. (CBS4) – A man has been convicted of causing a deadly accident by driving while high an marijuana.

Joshua Wittig, 18, was found guilty of vehicular homicide Thursday for hitting a motorcyclist near the intersection of Thornton Parkway and Steele Street in October. The judge ordered a complaint filed against the doctor who wrote Wittig’s prescription for medical marijuana

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The judge found that the Dr. Rita Starritt did not conduct any kind of physical examination or medical evaluation before approving the use of medical marijuana. Wittig went out and bought some before he killed 33-year-old John Hines.

“(He was) an exceptional friend to hundreds of people,” Hines’ sister Cara Hines said. “Literally every person he crossed paths with became better for it.”

An SUV driven by Wittig crossed over the center line. He admitted having used marijuana and other drugs a short time earlier.

“It was one of four or five drugs ingested into his system and I’m sure in combination with the Xanax it surely had an effect on him,” defense attorney Joseph Scheideler said.

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Starritt was seen at New Leaf Wellness in Boulder. Elizabeth Plummer is the owner.

“I don’t think that you should be extremely high or medicated and go out and drive a car just as I don’t think you should be extremely drunk and go out a drive a car,” Plummer said.

The jury agreed. Wittig was convicted of vehicular homicide under intoxication. His family members and friends left court in tears.

The defense had claimed Wittig needed the medication for a previous back injury and that the motorcyclist was intoxicated as well.

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Wittig faces up to 12 years in prison.