By Scott Sleek
Monitor staff

She sat through three months of testimony? some of it heart-wrenching but much of it arcane and tedious?in the trial of Oklahoma City bombing suspect Terry Nichols. Now, Diane Salerno, PsyD, questions whether the complexity of the evidence?or the way it was presented?is what ultimately led the jury to spare Nichols from a murder conviction and a death sentence.

Salerno, a clinical child psychologist in Denver, was one of six alternate jurors in Nichols? trial on charges that he helped Timothy McVeigh plot and carry out the 1995 bombing that killed 168 people.

Although she ultimately didn?t participate in the deliberations, Salerno says that prosecutors convinced her that Nichols was indeed guilty of first-degree murder, as charged. Yet even she grew fatigued listening to the massive amount of intricate chemistry and other forensic evidence the prosecution presented, despite the fact that she, by virtue of her training, had a greater grounding and interest in science than the other jurors.

She believes her experience casts light on a big problem with expert testimony: Even the most scientifically sound evidence may, when presented in court, exceed the jury?s comprehension or patience.

?Several jurors, I think, had trouble paying attention to the evidence, and I think that hurt the prosecution?s case in the end,? Salerno says about the trial.

The prosecutors had expert witnesses provide lengthy, tedious explanations about such issues as the explosive properties of the ammonium nitrate found in Nichols? garage, Salerno noted.

Even the most attentive jurors may have ended up discounting much of this evidence, simply because they didn?t understand it, she surmises.

?It was easy for the defense to point out errors and say the science was unreliable,? she adds. ?For me, one or two errors doesn?t mean you throw out the evidence completely. But jurors who have less experience with scientific evidence are likely to throw it out, or disconnect from it.?

The psychological literature lends some credence to her hypotheses about the jury?s reaction to the evidence. A study recently conducted by Princeton University psychologist Joel Cooper, PhD, and colleagues found that jurors are more likely to rely on the content of expert testimony when it is presented simply and clearly. When the testimony is more difficult to understand, the jurors focus on such cues as the expert witness? appearance or credentials to weigh the validity of the evidence, Cooper found. The study appears in Law and Human Behavior (1996, Vol. 20, No. 4, p. 379?394).

Salerno says she is disappointed that the jury convicted Nichols of the lesser charge of involuntary manslaughter, but respects the decision nonetheless. ?The verdict was a compromise,? she says. ?I think given the range of opinion people had on the jury, this was the best decision they could come to.?

(In the verdict handed down Dec. 23, the jury also found Nichols guilty of conspiracy to use a weapon of mass destruction. The jurors deadlockedon whether he should be sentenced to death, preventing the judge from sentencing him to anything more than life in prison.)

Salerno says her experience in the Nichols case has given her a new interest in the psychological aspects of jury selection and group dynamics. And she also has learned that many forensic experts need help communicating their data to the untrained ear.

?I?ve been telling some of my friends who are trial attorneys that their experts need to talk in lay terms and not belabor the details,? she says. ?Otherwise, the jury just won?t get it.?