The attorney for a West Jordan police officer charged with rape spent Friday afternoon quizzing a polygraph expert about the reliability and accuracy of the tests. The expert said the tests have evolved from primitive systems to sophisticated techniques that draw a great deal from medical science.

Defense attorney Ron Yengich is representing Bruce Eric Ballenger, a police officer now on leave who is facing two counts each of first-degree felony rape and second-degree forcible sexual abuse for allegedly attacking a woman on March 13. Ballenger maintains the two had consensual sex.Yengich spent much of the afternoon in 3rd District Judge Ronald Nehring's court questioning Steve Bartlett, a certified polygrapher and an investigator who has worked for the Salt Lake District Attorney's Office for 18 years.

Bartlett has headed the Utah Polygraph Association, participated in national organizations, won awards, taught polygraph procedures and conducted approximately 7,000 polygraph tests in the past 18 years.

Bartlett said that although polygraph tests "are not foolproof," it's his opinion that the tests are 98 percent accurate, based on studies that he has read.

"In the last 10 to 15 years, the instrumentation, techniques and application have changed," Bartlett said. "Previously, it was basically a blood pressure cuff."

Today, the machine and the questioning techniques are much more sophisticated.

A few professionally coached individuals could beat a polygraph test, but most people could not do so. Individuals sometimes try such tricks as contracting muscles or putting tacks in their shoes to alter their test results, but a trained polygrapher could usually detect that, he said.

A polygraph test was administered to Ballenger but the results were not disclosed in court Friday.

Under questioning by prosecutor Marsha Atkin, Bartlett conceeded that some experts consider the polygraph to be so unreliable that it should never be used.

Bartlett also responded to Atkin's questions by testifying that questions asked during a polygraph test can be very subjective and that certain phrases, such as "forcibly" could have different connotations to a police officer and an untrained person.

Nehring will hear more testimony on the issue when the hearing resumes Sept. 8.