The Air Force’s Office of Special Investigations noticed a problem as early as 2002, the year the LX4000 hit the market. A spokeswoman said her law enforcement agency was concerned that it could change the outcome of tests, and sought out Lafayette officials.

David Reisinger, a veteran federal polygrapher, said he first witnessed a problem with the LX4000 in 2005... Reisinger pressed the company to look into it because he saw it could change the outcome of a test depending on the setting.

He notified his supervisors, and Lafayette pledged to fix it. Years and dozens of examples later, the company still hadn’t, he said.

“I felt the manufacturer had given us the runaround and was never completely straightforward about what was going on,” Reisinger said. “I didn’t think we could trust them anymore.”