TROY, Mich. – Jeffrey Mosteller, the safety director at the Oxford Center in Troy, pleaded no contest Tuesday to involuntary manslaughter.
He’s the first of four defendants to take a plea more than a year after a deadly hyperbaric chamber explosion killed 5-year-old Thomas Cooper.
Under the sentencing agreement, Mosteller faces a range of 19 months to 15 years in prison. A second-degree murder charge was also dropped.
He is scheduled to be sentenced Aug. 31 before Judge Rowe.
Background on the explosion
The fatal explosion occurred Jan. 31, 2025, at the Oxford Center’s Troy facility. Thomas Cooper, 5, was killed, and his mother was severely injured.
Prosecutors say a spark of static electricity ignited a fire inside the pressurized, high-oxygen chamber, causing it to explode. According to testimony from safety experts and former employees, staff at the facility consistently ignored industry safety standards.
Alleged violations included failing to use grounding wrist straps, giving the child a blanket taken directly from a dryer, and tampering with the chamber’s cycle history.
Four defendants
The case involves four Oxford Center employees charged by Michigan Attorney General Dana Nessel’s office:
- Tamela Peterson, CEO and founder — charged with second-degree murder and involuntary manslaughter.
- Jeffrey Mosteller, safety director — pleaded no contest to involuntary manslaughter.
- Gary Marken, primary management assistant — charged with second-degree murder and involuntary manslaughter
- Aleta Moffitt, chamber operator — charged with involuntary manslaughter and intentionally entering false information into medical records.
Civil lawsuit
Beyond the criminal case, the Cooper family filed a $100 million wrongful death lawsuit through Fieger Law, naming eight defendants including all four individuals facing criminal charges, the Oxford Center itself and the chamber’s manufacturer.
James Harrington, an attorney with Fieger Law, said his team is closely monitoring the criminal proceedings.
“Once you start seeing some of these individuals take accountability, it’s probably just a matter of time before others follow suit,” Harrington said.
Harrington said that a no-contest plea serves as a de facto admission of responsibility in the civil case.
“This plea of the involuntary manslaughter is an admission of criminal negligence. In the civil case, it’s general negligence. So really this is an admission of fault, and we are now starting to see some of those involved take accountability,” Harrington said.
AG response
“A young child lost his life in a completely preventable tragedy because this defendant allowed an outdated device to operate in defiance of safety standards,” said Michigan Attorney General Dana Nessel. “While no outcome can reverse this loss, it is my hope that this conviction provides a sense of justice to Thomas’s family.”