'Innocent Until Proved Guilty?'

Crowe said the police used the machine to persuade him to confess and then to implicate two of his classmates.

"So I got a knife, and I went into her room, and I stabbed her," Crowe can be heard saying on tapes from his questioning.

But one week before the start of his trial, the police found DNA evidence that led to the real killer, a transient who is now in prison for killing Crowe's sister. The judge denounced both the false confession and Humble's machine.

"I don't believe the instrument was wrong. Now were the examiners wrong? I don't know," Humble replied when asked about the case. "I don't believe I owe Michael Crowe an apology."

'Nothing More Than a Prop'

But when the Crowe family sued Humble and his company, the National Institute for Truth Verification, the case was settled out of court. During a deposition, a top executive from Humble's company admitted under oath that the machine is not capable of detecting truth or lies.

"This device is nothing more than a prop," said John Palmatier, who earned a doctorate in psychology and who studied the machine for the Michigan State Police Department, where he worked. He said his study along with others found no scientific basis for Humble's claims.

"You could not accurately discriminate between truthful and deceptive subjects using that device," said Palmatier. As to whether the device could be used as a scare tactic, Palmatier answered, "Oh, exactly. Police officers have for years."

In his view, Palmatier said that explains the police endorsements that Humble puts in his promotional materials, citing one case after another solved with the stress-analyzer machine.

Humble said the machine can only really be tested in the field, where he said it has a 98 percent accuracy rate.

"We teach that it's an investigative tool. It's not meant for a detective to go out and get a search warrant or to get an arrest warrant," Humble said.

But that is not exactly what happened in Las Vegas in the case of Vincent Sedgwick, married with a young daughter. He was wrongly charged with rape, which carried a possible life sentence. His arrest warrant was based largely on his supposed failure on a CVSA test.