A psychiatrist plans to electronically scan the brain of Jeffrey L. Dahmer in an attempt to determine if he was criminally insane when he killed 17 people.

The psychiatrist, Dr. George B. Palermo, received permission on Friday from Circuit Judge Laurence C. Gram Jr., who will preside over Mr. Dahmer's trial in January, to make the scan.

Mr. Dahmer, 31 years old, has admitted killing 17 boys and young men, most of them in Wisconsin, in the past 13 years. He confessed to the killings after the remains of 11 people were found in his apartment in July. He has been charged with 15 murders in Milwaukee and has pleaded innocent by reason of insanity.

Mr. Dahmer's lawyer, Gerald Boyle, has said his client might forgo the guilt phase of the trial if evidence against him is overwhelming, and testimony about Mr. Dahmer's mental condition would form the bulk of the trial.

Dr. Palermo said he would use a CAT scan, which uses X-rays of soft tissues to form an image of the brain,in his analysis of Mr. Dahmer's brain.

Dr. Palermo wrote in his request that a complete psychological testing should be done, along with electronic scans of the brain and a chromosome analysis to provide an objective medical-psychiatric report.

Some specialists say chromosomes, which carry hereditary characteristics, are similar among the criminally insane and could indictate a person's tendency to criminal behavior.