How Brain Scans Are Used In Murder Trials

The functional magnetic resonance imaging (fMRI) brain scan of accused murderer Brian Dugan was introduced in the sentencing portion of his murder trial. The defense used the scan to try to demonstrate that the defendant's brain was psychopathic.

The main benefit of using fMRI to assess the brain of a defendant is that technicians can link active brain anatomy to different cognitive skills - like reasoning and decision-making. MRI (magnetic resonance imaging) shows only the brain's structure: fMRI shows how an individual's brain functions and thus relates more closely to thought and behavior.

From the standpoint of the courts, the debate over whether or not to use fMRI evidence has several dimensions. The first is simple: Can accurate, reliable evidence be obtained? On that score, fMRI appears to perform well. In research conducted at Temple University, scientists were able to distinguish truth tellers from liars with an accuracy of 92 percent.

In another experiment, designed by Joshua Greene and Joseph Paxton at Harvard University, volunteers were asked to bet money on a coin flip. Sometimes, they were given the opportunity to tell afterwards whether or not they had successfully predicted the outcome of the toss - and so they were given a chance to lie.

An fMRI was used to record brain activity in the prefrontal cortex and other regions associated with decision-making and behavioral control. Honest players showed no increase in brain activity even when they had the opportunity to cheat. However, liars' brains showed increased activity whenever they had a chance to cheat.

So, fMRI seems to work in laboratory settings. The real doubts begin to surface when considering whether or not the data will be good in the real world.

"When you build a model based on people in the laboratory, it may or may not be that applicable to someone who has practiced their lie over and over, or someone who has been accused of something," Elizabeth Phelps, a neuroscientist at New York University, told in March. "I don't think that we have any standard of evidence that this data is going to be reliable in the way that the courts should be admitting."

As it turned out, the brain scan was not admitted into evidence during the trial; it is recognized that courts are more lenient in introducing material in the sentencing portion of capital cases.

Science-fiction writers have been fascinated with the idea that technology that looks at brain activity could be used during a trial. For example, sf fans recall the dramatic (and highly visual) veridicator from H. Beam Piper's 1962 novel Little Fuzzy.

Robert Heinlein used this idea during a trial in his 1954 novel The Star Beast:

"'Mrs. Donahue, tell us what happened.'

"She sniffed. 'Well! I was lying down, trying to snatch a few minutes rest; I have so many responsibilities, clubs and charitable committees and things.'

"Greenberg was watching the truth meter over her head. The needle wobble restlessly, but did not kick over into the red enough to set off the warning buzzer..." (Read more about the truth meter)

From Wired.

(This Science Fiction in the News story used with permission of

Bill Christensen catalogues the inventions, technology and ideas of science fiction writers at his website, Technovelgy. He is a contributor to Live Science.