Testimony continued on Monday, Jan. 12, for the four people charged in the death of a 5-year-old boy killed in a hyperbaric chamber explosion in Troy nearly a year ago.

Most of the day was spent questioning a man referred to as Mr. McMullen, a former Oxford Center employee who left the company in 2021. The testimony focused on the use of a bracelet, or grounding strap, inside the hyperbaric chamber.

On Monday, the fifth day of the preliminary hearing, the defense attorney questioned whether it was a necessary safety step based on the medical manufacturer's in-person observations of the machine.

"Sechrist is seeing them (patients) without the bracelet, right? And they're not saying anything about it, right?" the defense attorney asked.

"Correct," McMullen said.

Previous testimony in December 2025 by the deputy fire chief of the Troy Fire Department concluded that the explosion that killed 5-year-old Thomas Cooper could have been avoided, citing static electricity as the cause.

While McMullen worked as a technician for many years with the company, he never set foot in troy facility. He testified that he tried raising safety concerns while with the company.

In addition to McMullen, two more witnesses were called before the end of the day.

The hearing is expected to continue on Tuesday.