Everyone agrees Brian Dugan is a psychopath.
At issue, however, is whether the killer has a brain defect that renders it impossible for him to control his violent impulses.
DuPage Circuit Judge George Bakalis agreed Tuesday to hold a hearing later this week to determine the reliability of novel scientific evidence Dugan's defense team wants to present as it tries to save his life.
Jurors earlier found Dugan is eligible for a death sentence for the Feb. 25, 1983 abduction, rape and murder of 10-year-old Jeanine Nicarico of Naperville. They still must decide his punishment - execution or life in prison without parole.
Dugan, 53, has been serving life terms since 1985 for two other sex slayings and a series of unrelated attacks on young women who survived.
One particular defense expert, Kent A. Kiehl, a forensic psychologist who conducts clinical neuroscience research on major mental illnesses, especially criminal psychopathy, claims Dugan shares similar abnormal brain function with other psychopaths he's studied. Kiehl uses a portable functional magnetic-resonance-imaging scanner, or fMRI, to measure brain function.
Kiehl argues psychopathy is caused by a defect in a network of brain regions that process emotion, inhibition and control. The main defect, known as "severe emotional detachment," is described as having a total lack of empathy and remorse.
Prosecutors are trying to bar such testimony. DuPage State's Attorney Joseph Birkett argued there is no evidence that Dugan has any brain damage and allowing confusing neurological testimony and color brain scan slides will mislead jurors.
"No one is going to dispute that Mr. Dugan sees a little girl and processes that information differently than the rest of us," Birkett said. "No one is going to dispute that Mr. Dugan was, is, and probably always will be a psychopath.
"He may process information differently, but he can understand what he's doing and he can control it. We shouldn't be using this courtroom as a clinic. It's (Kiehl's research) a hypothesis. It's not ready for prime time."
Defense attorney Matthew McQuaid countered that prosecutors are entitled to vigorously cross examine Kiehl.
"The brain of a psychopath is not a normal brain," McQuaid said, "and that's based on the behavior and emotional disability that they suffer. This is going to be important science down the road. It's not some kind of voodoo or just showing color slides (of Dugan's brain) to try to mislead the jury."
Judge Bakalis ruled he will allow a reliability hearing in which Kiehl and the prosecution's rebuttal expert will answer questions, likely Thursday, outside of the jury's presence. Bakalis is expected to rule afterward.