Stahl said she receives at least three to four polygraph administration requests each week and has conducted examinations in criminal cases ranging from child abuse to homicides, with results that vary from identifying a suspect to weeding out suspects.

“In some situations, a polygraph can make or break a case,” she said. “In some situations, it just gives investigators a better idea or better perspective on where they need to head with their investigation.”

Stahl said a polygraph test also can differentiate between people unrelated to a crime.

“It can eliminate truthful people that are innocent and have nothing to do with the crime,” she said.

A polygraph analyst looks for deception by comparing a person’s physiological attributes during questioning to their normal levels, said Lynn Marcy, director of the American Institute of Polygraph in Otsego, Mich. The examination’s accuracy depends on the ability of the analyst, he said.

“It’s like any other kind of a diagnostic or art form,” he said. “Some folks can be better at it than others.”

Stahl, who was trained as an analyst about three years ago, is very talented in her line of work, MSU police Sgt. Florene McGlothian-Taylor said. Stahl was sent to training by the MSU Police Department because there was a need for the services of a polygraph analyst within the community, McGlothian-Taylor said.

In many cases, a polygraph test can be very helpful to investigators because a person being tested by a polygraph analyst often will confess to a crime, Bob Kullman, a forensic examiner at Speckin Forensic Laboratories in Okemos said.

“There’s been many, many times where during the polygraph, the polygraphist will say, ‘You failed,’ and the suspect will say, ‘OK, I helped so-and-so bury the body,’” he said.

And if an examination does not lead investigators to a confession, it can show investigators if they are moving toward a suspect, Stahl said.

“It can be tremendously helpful,” she said.