But, after hearing two weeks of bombshell evidence about the days surrounding the massacre – and after 10 hours of deliberations – the jury found the 45-year-old guilty of all charges.
Her husband James Crumbley is set to be tried separately in March on the same charges. He has also pleaded not guilty.
From an extramarital affair to Taylor Swift quotes, here are the key revelations from Ms Crumbley’s trial:
The trial got off to an interesting start when Ms Crumbley’s attorney Shannon Smith quoted Taylor Swift’s song “Bad Blood” in her opening statement. Ms Smith said this case was about the prosecution “attempting to put a Band-Aid on problems that can’t be fixed with a Band-Aid”.
“A Band-Aid will never bring back the lives that were lost,” she added.
The defence attorney also insisted that Ethan’s mental condition was “not on her radar”, yet also described her as a “hypervigilant” mother. Ms Smith also emphasised Mr Crumbley’s love of guns and placed blame on the school.
The prosecution, by contrast, argued in its opening statement that Ms Crumbley was well aware of her son’s “deteriorating mental health”.
Despite this, she and her husband purchased a gun for him and took him to a shooting range. While there, the defence said, her son showed her how to use the gun.
“Jennifer Crumbley didn’t pull the trigger that day. But she’s responsible for their deaths,” Oakland County assistant prosecutor Marc Keast said.
Just before opening statements, there was also a dramatic moment in the courtroom when Ms Crumbley’s friend was removed from the courtroom.
Chilling shooting footage played in court
Ms Crumbley broke down in tears while the court was shown video footage of her 15-year-old son pointing his weapon at teachers and classmates in his high school.
The defendant’s sobs sparked a heated exchange among the attorneys.
The prosecution took issue with the response from Ms Crumbley — and her lawyer Ms Smith — to the footage, arguing they were not adhering to the court’s instructions to try to remain composed.
“You’re concerned about the influence of the jury. I take no issue with it. But it was a difficult thing and we’re doing it,” Oakland County Prosecutor Karen McDonald told the judge. “And then to have not just the defendant, her lawyer sobbing.”
Ms Smith interjected: “I did not sob.” She told the judge that this footage isn’t relevant to her client’s case and added that her team has never seen it before.
“We were not sobbing or making a scene. All my eye makeup is still on,” she said.
“Everyone here is human,” Judge Cheryl Matthews said, underscoring that she’s “striving for a fair trial.” The judge added: “I’m not a robot. I’m trying to keep myself from sobbing. I’ll do it at six tonight.”
Video shows Crumbley parents’ arrest
The court was shown police bodycam footage from the early hours of 4 December 2021, capturing the moment when authorities burst into a dark, industrial-looking room to arrest Jennifer and James Crumbley who were sleeping on a mattress on the floor.
The Crumbleys had been asked to turn themselves into authorities the day prior.
As a manhunt ensued, they were tracked down to Ms Crumbley’s friend’s artist studio.
In the video, the officers are seen pointing their guns at the couple.
“Let me see these hands!” the officers shout.
Mr Crumbley is heard screaming and seemingly struggling to stand on his own two feet. “Stand up!” an officer yells at him. When officers ask him his name he says, “James”. When they press him “James what?”, he replies with an exhausted, “Crumbley”.
Body camera footage then shows a fleet of officers investigating the room.
The police interview admission
On the morning of the shooting, school staff had grown increasingly concerned after finding Ethan’s drawing, depicting a semiautomatic handgun pointing at the words “the thoughts won’t stop help me”.
The Crumbley parents were called in to meet with school staff and their son to discuss it.
While given the choice of whether to keep Ethan in school or take him home, the parents opted for him to return to class. He shot up his school hours later.
A videotaped interview in the hours after the shooting shows investigators asking the parents about this meeting.
Mr Crumbley says their son was “doodling on a test or a practice test,” seemingly referring to the disturbing drawing, when Ms Crumbley interrupts: “I think we probably should have a lawyer.”
Mr Crumbley then says: “I think we can speak to the cops.”
Later in the interview, Ms Crumbley is seen telling police that the school counsellor “didn’t seem worried” about the drawing and that Ethan could either stay at school or his parents could take him home.
“And I really wish we took him home,” she is heard admitting.
Mr Crumbley also says at the start of the interview that he is “freaking out” and asks for some water.
He later tells police that their 15-year-old is a “great kid,” adding that he “doesn’t get in trouble at school”.
When an officer tells the parents that they will need to talk to Ethan, an emotional Ms Crumbley is heard asking: “Why?... He’s never done anything bad”.
The interview also revealed that Ethan had texted his mother — telling her that he loved her — not long before he opened fire on his classmates.
During the interview, Mr Crumbley also shares details with police about where his son had gotten hold of the gun.
He says that the weapon was hidden in a gun case in an armoire and that the bullets were “in a completely different spot underneath some jeans”.
Brian Meloche, a long-time friend of Ms Crumbley who had an affair with her in 2021, took the stand and told the court about his relationship with the convicted shooter’s mother.
After her son opened fire inside the school, Ms Crumbley texted Mr Meloche that the massacre “could have been prevented,” according to a message revealed in court.
Separate messages showed her describing the school’s response to Ethan’s disturbing behaviour – such as drawing a doodle of a mass shooting or searching online for ammunition – as “nonchalant”.
Despite both the Crumbley parents allegedly citing that they had jobs to return to and so couldn’t take him out of school on the morning of the shooting, Ms Crumbley messaged Mr Meloche saying that she could meet up with him, he testified.
Texts also revealed that Ms Crumbley said she wished the school wouldn’t have allowed him to stay in school.
Mr Meloche also told the court that Ms Crumbley told him on the day of the shooting that she realised the gun was gone from their home. He suggested she notify the police, he said.
She also texted him saying: “I failed as a parent, I failed miserably.”
As well as her affair with Mr Meloche, it emerged during Ms Crumbley’s cross-examination that she had been using the site AdultFriendFinder.
The website describes it as the “world’s largest dating and social network for adults”. She didn’t deny talking to others on the website, but no further details about those conversations were revealed.
‘Wish he would’ve killed us instead’
Ms Crumbley took the stand to testify in her own defence.
Her voice quivered as she talked about the day of the shooting.
“I couldn’t believe he had actually shot anybody in the school,” she said, adding that the whole situation felt “surreal.”
“That was the hardest thing I had to stomach – that my child harmed and killed other people,” Ms Crumbley said, stumbling over the last few words and uttering them quietly.
Although she spent most of her time on the stand on Thursday making direct eye contact either with her attorney or the jury box, when she mentioned her son’s shooting, she looked down, avoiding eye contact with anyone.
Her attorney also asked whether Ms Crumbley thought her son was a danger to others, she said: “As a parent you spend your whole life trying to protect your child from other dangers. You never would think you’d have to protect your child from harming somebody else.”
The 45-year-old was then asked whether she considered herself a victim. She said no because she didn’t want to “disrespect those families that truly are the victims”. She then added: “We did lose a lot.”
In the last few moments of the defence’s questioning on Thursday, she was asked whether she could change what had happened if she could. Ms Crumbley said, “Oh absolutely. I wish he would’ve killed us instead.”