A driver who had been smoking cannabis pulled out in front of a lorry - causing a crash in which his 18-year-old rear seat passenger died.
BMW driver John King, aged 32, was jailed for 12 months after he admitted causing the death of teenager Luke Hardwick by careless driving.
Sheffield Crown Court heard King had got lost going for a job interview and had pulled into a lay-by.
When he set off again he pulled out and collided with a seven-tonne scaffolding lorry.
His girlfriend at the time, Natalie Hardwick - Luke’s sister - suffered severe bruising, and her 19-month-old daughter Lily suffered life-threatening spinal and internal injuries, but has since recovered.
The couple have now split up.
Richard Clews, prosecuting, said the accident happened at 12.20pm last December 20 on the A638 near Doncaster.
King set off from his home in Toll Bar Road, Swinton, and picked up his passengers on the way.
Luke Hardwick suffered fatal injuries and died at the scene.
The court heard cannabis was found in King’s system when he was tested at the police station.
Cannabis was also discovered in the BMW, and King has previous convictions for possessing and producing the drug.
Dermot Hughes, defending him, said the death weighed heavily on his conscience and he was normally a ‘caring’ man.
He added: “It was not him having no regard for the rules of the road - it was momentary inattention.”
Judge Robert Moore banned King from driving for two years. He said the offence was aggravated by the fact he had taken cannabis.
He said: “You pulled into a lay-by, did a U-turn, and the rear offside of your car was crushed and a young man died.”