The mother of a teenage boy who gunned down four students at a US high school took the stand for the second day of testimony in her high-profile trial on manslaughter charges on Friday.

Jennifer Crumbley, 45, and her husband James Crumbley, 47, have both been charged with four counts of manslaughter. They are reportedly the first parents of a school shooter in the United States to face felony charges for their children’s actions.

Their 17-year-old son, Ethan Crumbley, is serving a life sentence for the November 2021 shooting at Oxford High School in Michigan that killed four students aged 14 to 17.

During the trial, Jennifer’s longtime friend Brian Meloche said the two had been having an affair when Ethan carried out the school shooting. She testified Thursday that they were having an affair.

Jennifer and Fire Chief Brian also reportedly hosted sex parties at the hotel.

They would often find strangers on a swinger app called “Adult Friend Finder” and arrange to “meet” them at hotels after get off work, according to prosecutors cited in the New York Post.

Jennifer admitted to using the app to “arrange for other people to meet us there,” but claimed she was going to a hotel after get off work “for a business trip,” the report said.

Prosecutor says Jennifer Crumbley was responsible for son’s school shooting

Earlier Thursday, Michigan prosecutors told jurors that Jennifer Crumbley failed to do several “tragic, small, simple things” that could have prevented the deaths of four people.

Prosecutor Mark Kester told jurors at the opening of the trial that Jennifer knew her son was in a “downward spiral” mentally and that only she and her husband could have known about the danger Ethan posed to others and that he had access to gun.

“The evidence will tell you that she didn’t pull the trigger, but she was responsible for these deaths,” Kester said.

“She didn’t do any of the sadly small and simple things to prevent this from happening,” he added.

Jennifer Crumbley’s defense attorney, Shannon Smith, opened the trial and said her client had no idea her son would kill four of his classmates.

“Jennifer Crumbley is the mother of a 15-year-old son who, in any event, was unaware that her son had any mental disorder or that her son would bring a gun into school or that Her son would shoot. People,” Smith told jurors.

Smith added that it was James Crubley, not Jennifer, who was responsible for making sure the gun Ethan used in the shooting had a trigger lock.