When Peter Braunstein was put on trial last year for a twisted Halloween torture attack, his lawyers used a visual aid to suggest that his actions were the product of mental illness.

It was a scan of the defendant's brain. A doctor testified that the patterns it revealed indicated that Braunstein, accused of donning a firefighter's costume and imprisoning a woman for 13 hours, suffered from schizophrenia.

The New York trial was one of a growing number of instances in which cutting-edge neuroscience has found its way into U.S. courts.

Brain scans have emerged as potentially powerful tools in battles over defendants' sanity. More defense attorneys are seeking scans showing brain damage or abnormalities that might have made it difficult for their clients to control violent impulses.

And experts say there is much more to come — including a few things that seem the stuff of science fiction. Within years, brain scans might be capable of serving as reliable lie detectors. Similar tests could potentially show whether a plaintiff in a personal injury case is really in pain, or faking it for sympathy, and brain images might even help jurors assess the reliability of a witness's memory.