Camp Verde, Arizona (CNN) -- Scott Barratt testified Thursday he felt nauseous, incoherent and "extremely uncomfortable" during a 2009 Arizona sweat lodge ceremony.
Barratt, a general contractor from Spokane, Washington, told jurors at the manslaughter trial of self-help author James Ray he tried to assist a fellow participant who was not moving during the event.
Ray asked for someone else to move the woman, Barratt said. Barratt testified he tried to do so, but that Ray told him to leave her in place because he got too close to the hot rocks when he tried to help. The woman, who Barratt thought might be unconscious, was left in place as the ceremony continued.
The woman, identified as "Linda," was not one of three fatalities in the ceremony.
Ray is accused of manslaughter in the deaths at his October 2009 "Spiritual Warrior" retreat in the desert. At least 15 others who took part in the sweat lodge ceremony became ill. More than 40 others were uninjured.
Prosecutors argue that the lodge -- made of willow trees and branches, and covered with tarpaulins and blankets -- was heated to a perilously high temperature, causing the participants to suffer dehydration and heatstroke.
The sweat lodge ceremony consisted of eight rounds, with each round lasting 10 to 15 minutes. While they were not prevented from leaving, participants have said they were told to wait until the breaks between rounds.
Barratt acknowledged he had free choice during the activities.
"It's my free choice but it's also the peer pressure that kind of keeps you there, plus my own desires to play the game correctly," said the former Army helicopter pilot who was trained as a medic.
The prosecution witness left the lodge once because of the extreme heat, but returned.
Barratt testified that if he'd been thinking clearly he probably wouldn't have gone back in.
His testimony continues Friday.
The event participants paid up to $10,000 to seek "new areas of consciousness," according to testimony.
Many, like Barratt, had attended previous James Ray International seminars, believing they would become a better person and, in several cases, more effective in business.
"I'm very grateful for what I learned from James," Barratt said under cross-examination.
Ray's attorneys have argued that exposure to an unknown toxin, perhaps a pesticide, in the lodge could have caused the fatalities.
In Session's Michael Christian contributed to this report.