Michael Napier, a former FBI profiler and polygraph examiner, said the way the test was administered will help determine whether the Ramseys were telling the truth when they said they had no involvement in the slaying of their 6-year-old daughter JonBenet.
It's critical that the examiner ask simple, direct questions that allow no "wiggle room," Napier said.
He said an inexperienced examiner could misinterpret readings that tell whether subjects' blood pressure, breathing patterns and level of perspiration change with an attempted deception — indicators the test relies on to root out deception.
Authorities still consider the parents the prime suspects in the Christmas 1996 slaying of their daughter in their Boulder, Colo., home. The Ramseys offered to prove their innocence through a lie test, but Boulder authorities insisted it be administered by the FBI.
But the Ramseys, saying the FBI was biased against them, arranged to take a test in their new hometown of Atlanta. An independent examiner, Ed Gelb, conducted the polygraph.
At a Wednesday afternoon press conference, Gelb said the test revealed that neither Ramsey lied when answering questions about their daughter's murder. The couple said the results were final, definite proof that they were not involved in Jon Benet's death.
Gelb's experience and qualifications, and the kinds of questions he asked, are all-important in determining the validity of the tests, Napier said.
He said that if the questions are poorly fashioned, or thought up by the subjects themselves, their answers can be shaped to get to a predetermined result.
"Let's say you have a barroom brawl where A strikes B," Napier said. "B falls down and A leaves the bar and B later dies. If the examiner asks A, 'Did you cause the death of B?', he could think I don't know exactly what killed B and he could say no.
"But if you asked, 'Did you strike B and was B on the floor when you left?', that would be a better question."
Attorneys for the Ramsey did not produce Gelb's qualifications or a list of questions asked in the test during Wednesday's press conference.
And even if the lie-detector test is certified by both sides as completely accurate, Napier said, the notoriety of the case will ensure that the Ramseys will never be able to fully escape suspicion.
"[The] questions will not go away with a case like this for a long time," he said.