Oxford High School shooting case: Prosecution, defense spar over expert witnesses

PONTIAC, Mich. (FOX 2) - Defense attorneys for James and Jennifer Crumbley sought to poke holes in the testimony of two expert witnesses called by the prosecution during a pre-trial hearing Friday.

The witnesses - Dr. Jillian Peterson of Hamline University and Dr. Dewey Cornell of the University of Virginia - both have research backgrounds in mass shootings and methods that could prevent mass shootings. 

While in court, both academics explained their research and how it pertained to mass shootings with a focus on mass school shootings. Both emphasized that mass shootings could not be predicted, but could be prevented.

"We can't predict where lightning will strike, but we know we don't want to get in a swimming pool in a storm," said Cornell, who has testified on mass shootings in Congress and authored dozens of studies on the field. 

Peterson, who has never testified in court before Oct. 28, has worked to understand the life histories of mass shooters, the patterns they exhibit prior to carrying out the shooting, and publishing data that public and private groups could use as they work to prevent school shootings as well.

Her work has culminated in a book titled "The Violence Project" as well as the creation of a working model for understanding the stages that particularly school shooters undergo prior to the carrying out the act. 

The pre-trial hearing before Judge Cheryl Matthews was for whether the prosecution could call the witnesses to testify for the pending trial of Ethan Crumbley's parents, who are both charged with four counts of involuntary manslaughter for their son's involvement in the Oxford High School mass shooting. 

Matthews said she would issue an opinion on whether she'll admit the experts to testify within 7-10 days. 

More Oxford High School shooting news:

• Crumbley parents trial set for January as Ethan pleads guilty
• Phone records show Jennifer ignored texts from Ethan about demons
• Ethan Crumbley says he gave James Crumbley money to buy gun used in Oxford High School shooting

Pathway to violence

Mass school shooters "don't snap" when they begin shooting, Peterson said. Instead, a "slow build-up" happens before individuals reach a "crisis point" where their behavior changes. At this point, individuals will have reached a state of mind where they lose the ability to cope with problems in their lives. 

They begin to isolate more and individuals might notice a change in their demeanor, Peterson said. 

"It looks different in each individual," she said

At this stage, school shooters exhibit a behavior called "leakage" where they reveal their plans to someone else. It can be an obvious leak, like telling someone about plans to bring a gun to school and start shooting - or more subtle like drawing guns on a piece of paper. 

While leakage isn't as common during mass shootings of all varieties, they appear in most cases involving K-12 settings, Peterson testified, citing data from a grant project she received from the Department of Justice.

"Leakage is a really critical intervention point. It's more of a cry for help," Peterson said. 

Intervention points for Ethan Crumbley

Peterson saw multiple opportunities where individuals could have prevented the Oxford High School mass shooting. Two moments stood out to the researcher, who had been provided background on Ethan Crumbley and the shooting that unfolded Nov. 30. 

The first incident was March 2021, when Ethan Crumbley mentioned having hallucinations and delusions. The second was a month before the shooting when his behavior changed. His best friend had left and his dog had died. 

He reached his crisis point as evident by entries in his journal, Peterson said. 

It's not clear who if anyone had seen the journal, but neither James nor Jennifer have said they had read through it before Ethan went to school the day the shooting happened.