PROVO — On Oct. 8, 1995, Christopher Jeppson took a polygraph test and passed, with the results written as "no deception indicated."
Jeppson told the FBI investigator he didn't cause 15-year-old Kiplyn Davis' disappearance, nor was he responsible for her missing status.
After several rounds of the specially designed, eight-question test, the examiner let Jeppson go, having concluded he was telling the truth.
And that's what Jeppson's attorneys want jurors to hear while they're considering whether Jeppson should be convicted of Davis' murder.
"The only evidence (the state) wants to admit is joking statements," said Jeppson's attorney, Scott Williams. "This is a scientific test, scientifically analyzed to be truthful."
There is no forensic evidence in the case, as Davis' body has never been found.
Jeppson and fellow classmate Timmy Brent Olsen were charged based on statements they made to other people regarding their involvement in Davis' failure to return home from school on May 2, 1995.
The 4th District Court hearing regarding the admissibility of Jeppson's polygraph test has been continued until May, when the state's expert witness will testify against such an admission.
But all day Tuesday, Jeppson's attorneys presented evidence about the reliability and validity of such tests, and why Jeppson's passed polygraph should be admitted into evidence at the upcoming trial.
"If (Jeppson) had had any involvement, I certainly would not expect to see charts like this," said David C. Raskin, an emeritus professor of psychology at the University of Utah and a forensic psychological consultant.
Raskin specializes in psychophysiology, studying psychological processes and mental states by reviewing bodily reactions in certain situations. For decades he has focused on polygraphs, both in developing scientifically proven methods for administering them as well as reviewing and scoring them.
But prosecutors are skeptical of their trustworthiness.
During cross examination, prosecutor Sherry Ragan asked Raskin whether Jeppson's polygraph test included any mention of a "murder."
Raskin said no. The wording focused on a kidnapping or a missing person, he said.
"As I understand it, at that stage, nobody seemed to know what might have happened to her. Everything was speculation," Raskin said. "All that was known was that she disappeared."
Ragan also asked if Jeppson could have misunderstood the questions.
"If (he) were only one of several people involved, he might not feel responsible for her disappearance," she said. "What I'm saying is we don't know how he interpreted that question."
However, Raskin said any involvement or knowledge in Kiplyn's disappearance would have caused Jeppson trouble in answering two of the eight questions:
"Did you cause the disappearance of Kiplyn Davis on May 2?" and "Are you responsible for the disappearance of Kiplyn on May 2?"
Jeppson answered "no" to both.
Two other questions were comparison questions, asking whether Jeppson had ever lied before to someone who trusted him, and if he had lied to his friends. The four other questions were ice breakers or neutral questions.
By comparing an individual's physical reactions to the relevant questions with the physical reactions to the comparison questions, test examiners then assign positive or negative scores, which indicate deceptiveness or non-deceptiveness.
E-mail: [email protected]