Washington DC - The father of a teen who purchased the gun that his son used in a deadly 2021 school shooting was found guilty of involuntary manslaughter in a Michigan court on Thursday.

James Crumbley and his wife, who was found guilty of the same charges last month, bought their then 15-year-old son the 9mm SIG Sauer handgun that he used to kill four students at Oxford High School, 45 miles north of Detroit.

The Crumbleys, the first parents of a school shooter to face felony manslaughter charges in the United States for the actions of their child, were accused of ignoring warnings that the teen had mental health struggles.

"James Crumbley failed his son in a tragic way," prosecutor Karen McDonald said in closing arguments.

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"But he didn't just fail his son. He failed to perform his legal duty to prevent these kids from being killed."

But defense attorney Mariell Lehman said James Crumbley "did not know he had to protect others from his son. He had no idea what his son was planning to do."

The jury returned a guilty verdict for James Crumbley (47) after just over a day of deliberations.

Both parents face up to 15 years in prison.

Their son Ethan is serving a life sentence for the November 30, 2021, shooting which left four students dead and seven other people injured.

Jennifer Crumbley (45) testified during her separate trial that her husband bought their son the gun just days before the attack as an early Christmas present and that she took the boy to a shooting range the next day.

She said her husband was responsible for storing the weapon at their home, and it was for her son "to use at the shooting range only."

The mother said she never had reason to believe her son was capable of carrying out such a violent act.

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The Crumbleys were summoned to the school on the day of the shooting – before it occurred – after a teacher was "alarmed" by a violent drawing she found on Ethan's desk.

The parents were shown the drawing and advised they needed to get the boy into counseling. They 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 6-year-old son shot and severely wounded his teacher was recently sentenced to two years in prison for felony child neglect and 21 months in prison after pleading guilty to illegally obtaining the firearm.