The parents of a teenager who carried out a deadly school shooting in the US state of Michigan were sentenced to 10 to 15 years in prison on Tuesday in an unprecedented and closely watched case.

Jennifer Crumbley, 46, and her husband James, 47, were the first parents of a school shooter convicted of involuntary manslaughter in the United States for the actions of their child.

Oakland County Circuit Court Judge Cheryl Matthews sentenced them to 10 and 15 years in prison each with credit for the 28 months they had already spent behind bars.

Their son Ethan, who is now 17, is serving a life sentence for the November 30, 2021, shooting which left four students dead and seven other people injured at Oxford High School, 45 miles (70 kilometers) north of Detroit.

"Parents are not expected to be psychic," Matthews said at an emotional sentencing hearing in Pontiac, Michigan, attended by parents of the victims.

"But these convictions are not about poor parenting," Matthews said. "These convictions confirm repeated acts, or lack of acts, that could have halted an oncoming runaway train."

Addressing the court before sentencing, Craig Shilling, the father of Justin Shilling, 17, one of the slain students, told the Crumbleys "The blood of our children is on your hands."

Steve St. Juliana, the father of another victim, Hana St. Juliana, who was 14, said her murder "has destroyed a large portion of my soul."

"I am forever denied the chance to hold her or her future children in my arms," he said.

  'Alarmed' 

 During separate trials, the Crumbleys were accused of ignoring warnings that their son had mental health struggles.

Jennifer Crumbley testified during her trial that her husband bought their son the 9mm SIG Sauer handgun he used in the attack just days earlier as an early Christmas present.

She took the boy to a shooting range the day after the purchase.

The Crumbleys were summoned to the school on the day of the shooting itself after a teacher became alarmed by a violent drawing she found on Ethan's desk.

They were shown the drawing and advised they needed to get the boy into counseling. The parents allegedly resisted taking their son home and he returned to class.

He later entered a bathroom, emerged with the gun which had been concealed in his backpack, and fired more than 30 shots.

Amid a huge number of deadly firearms incidents involving young people in the United States, pressure has been mounting to punish parents who make it possible for their children to get weapons.

The father of an Illinois man accused of killing seven people in July 2022 pleaded guilty in November to misdemeanor charges of "reckless conduct" for helping his son obtain the assault rifle used in the mass shooting.

A Virginia woman whose six-year-old son shot and severely wounded his teacher was recently sentenced to two years in prison for felony child neglect. She later received an additional 21 months in prison after pleading guilty to illegally obtaining the firearm.