Prosecutors accuse both James and Jennifer Crumbley of ignoring signs their son had mental health issues and instead gifting him with the handgun he used to kill four classmates at Oxford High.
The parents faced separate trials; James Crumbley’s begins next month.
But his defense is arguing the same point his wife’s attorneys did, that certain evidence could un-fairly prejudice a jury against their client.
That includes graphic pictures and video of the killings, and the testimony of students who were shot during the attack.
Each charge of involuntary manslaughter carries a maximum of 15 years in prison.
Jennifer Crumbley’s sentencing is set for April.