James Crumbley “did nothing” to prevent his son from carrying out Michigan’s deadliest school shooting, prosecutors said in closing arguments on Wednesday, while his defense attorney argued that he was unaware of his son’s troubled mental state or plans to attack his schoolmates.

A jury must now decide whether Mr. Crumbley should be held partially responsible for his son’s rampage, which killed four people and injured seven others. The boy’s mother, Jennifer Crumbley, was convicted last month by a different jury in the same courtroom.

Prosecutors took the rare step of bringing criminal charges against the Crumbleys for the shooting at Oxford High School on Nov. 30, 2021. They accused Mr. Crumbley of missing cries for help from his son, Ethan, who was 15 at the time and complaining of mental health issues, and of failing to secure the gun used in the shooting.

“James Crumbley was presented with the easiest, most glaring opportunities to prevent the deaths of these four students,” Karen McDonald, the prosecutor in Oakland County, said in closing arguments. “And he did nothing.”

Mariell Lehman, Mr. Crumbley’s defense lawyer, told the jury that prosecutors had left plenty of room for reasonable doubt. “You heard no testimony, and you saw no evidence, that James had any knowledge that his son was a danger to anyone,” she said.

Mr. Crumbley has been in jail since December 2021, when he and his wife were each charged with four counts of involuntary manslaughter for the deaths of Madisyn Baldwin, 17; Tate Myre, 16; Justin Shilling, 17; and Hana St. Juliana, 14. The couple requested separate trials. Unlike his wife, Mr. Crumbley chose not to testify in his own defense.