OAKLAND COUNTY, Mich. – The prosecution and defense attorneys gave closing arguments Tuesday in the preliminary hearing against the four Oxford Center workers charged in the hyperbaric chamber explosion death of a 5-year-old boy, and the judge said she needs more time to decide whether to bind the case over.
Tamela Peterson, 59, of Brighton, Jeffrey Mosteller, 65, of Clinton Township, Gary Marken, 66, of Spring Arbor and Aleta Moffitt, 61, of Rochester Hills, were charged after Thomas Cooper was killed when the hyperbaric chamber he was receiving treatment in exploded at the Oxford Center in Troy on Jan. 31, 2025. The boy’s mother was also injured in the explosion.
Recommended Videos
Peterson, the Oxford Center’s founder and CEO, along with Mosteller, the safety manager, and Marken, the primary management assistant, were charged with second-degree murder. They were also given the alternative charge of involuntary manslaughter, which means that a jury will decide which charge accurately fits their conduct.
Moffitt, who was allegedly operating the hyperbaric chamber at the time of the explosion, was charged with involuntary manslaughter and falsifying medical records.
On Tuesday, Jan. 20, 2026, 52-4 District Court Judge Maureen McGinnis said she needed more time to make her decision on whether or not to bind the case over to circuit court.
Assistant Attorney General Chris Kessel argued prosecutors met their burden to show probable cause that Oxford Center leaders knowingly ignored life-threatening risks, resulting in the boy’s death.
According to Kessel, the Oxford Center repeatedly violated industry safety rules, most critically by allowing patients to undergo treatment without grounding wrist straps in hyperbaric chambers, despite NFPA 99 standards, Sechrist manufacturer warnings, and expert testimony that ungrounded patients face a fire risk.
Kessel highlighted evidence that technicians were stretched thin and overseeing up to five chambers at a time, chambers went years without required maintenance, safety pauses and pat-downs were skipped, and prohibited polyester materials were used.
Experts testified that in a monoplace chamber, “fire means death,” and investigators concluded static electricity was the only reasonable ignition source. Video evidence, Kessel said, shows Thomas moving in the chamber, ungrounded, moments before flames erupted near his knee.
Kessel also argued that Peterson, Marken and Mosteller all knew the risks and upheld unsafe practices. Marken, Kessel argued, was more than a facilities manager, citing testimony that he handled chamber maintenance issues and was seen manipulating a chamber’s dive counter.
Mosteller, Kessel said, conducted a scientifically meaningless “experiment” to justify eliminating wrist straps, despite knowing a hyperactive child faced heightened risk.
Defense attorneys countered that the case rests on speculation, not proof.
Peterson’s attorney, Thomas Cranmer, argued the fire’s cause remains unproven, noting Fire Chief Hugg admitted there is no direct evidence the blaze originated from skin-level static and that his investigation remains open. He warned the court against charging Peterson based on her status as CEO, arguing she reasonably relied on her safety director’s judgment and even personally underwent treatment without wrist straps—evidence, he said, of an honest belief they were unnecessary.
Todd Flood, Marken’s attorney, argued there was no evidence his client had any duty over hyperbaric safety or patient care, portraying him strictly as a facilities manager who fixed lights and toilets, not chambers. Witnesses, he said, consistently testified Marken was not involved in treatment decisions and was not present at the Troy facility.
Mosteller’s attorney, Alona Sharon, said the no-wrist-strap policy was already in place at the Oxford Center when her client started working there and that he raised concerns about it.
She argued that Mosteller investigated the issue, conducted grounding tests with a multimeter, and reasonably concluded the patient was grounded through the mattress.
The defense emphasized that more than 100,000 dives occurred without wrist straps and that experts disagreed on whether a single static spark could ignite cotton without an additional volatile substance.
Aleta Moffitt’s attorney, Ellen Michaels, argued the technician followed her training exactly and had no knowledge that wrist straps were required or that failing to use them posed a deadly risk. She called it unjust to charge a low-level employee who was “heroic” in her response after the explosion and emotionally devastated by the child’s death.
In rebuttal, Kessel said disputes over expert opinions do not erase probable cause.
He argued Peterson is charged not for being CEO, but for creating and enforcing a policy that removed grounding straps to speed treatment.
He dismissed the defense experiments as unreasonable and said that when Sechrist told Peterson the chamber was over 20,000, so they would no longer maintenance it. She responded the next day, asked for documentation, and when Sechrist sent it, Peterson told the company that the chamber had been sold and replaced. Kessel said that the chamber was actually never sold and continued to be used.
Kessel responded to Michaels’ argument about how Moffitt didn’t know the grounding wrists were required because she wasn’t told to use them during training, and wasn’t required to take the safety director’s course or read the materials with that.
“Ms. Michaels said that Ms. Moffitt is not trained in this, she’s not certified in this, she’s not an accomplished person doing this, she’s not licensed. Then what is she doing doing these treatments, judge? If you don’t know what you’re doing, which kind of sounded like Ms. Michaels’ argument, then you have no business putting someone through treatments that ultimately could result in their death,” Kessel said.
The judge said she needed more time to make her decision on whether to bind the case over to circuit court, where the defendants could face trial.
McGinnis said she feels like she’s well aware of the evidence, but she wants to apply what was said in the arguments, including the cases that were cited, and determine if they apply to their arguments in ways that would impact her decision for or against binding the case over.
“I have the intention of reaching a decision quickly, but I cannot take all of the information that I’ve heard from your arguments and apply them appropriately to all of the testimony, even though I have spent considerable time since we concluded, reviewing everything,” McGinnis said.
The judge said she doesn’t have an exact date for when she’ll issue the opinion, but said, “I do need a little bit of time to take everything that I’ve heard today and determine how it will apply to my decision.”
On Tuesday, Peterson was also charged with nine counts of health care fraud. According to the Michigan Attorney General Dana Nessel’s office, Peterson was aware of fraudulent billing practices and personally benefited from them, including claims submitted for services that were never provided.
Read: CEO of Troy center where boy died in hyperbaric chamber now facing health care fraud charges
For a full deep dive into what we learned during previous days of the preliminary hearing, check out the following stories: