Has he talked in the 25 years since the slaying? Has he tried to ease his conscience by telling relatives or friends about the death of Sister Catherine Ann Cesnik, a popular high school teacher who was killed and dumped in a Lansdowne field?
Baltimore County police hope the killer has mentioned the slaying to someone.
In renewing their efforts to solve the crime, they have speculated that it was a crime of opportunity, a robbery committed by a stranger who might not have known that his victim was a nun.
Detectives ask that citizens recognizing anything in their criminal profile call Baltimore County police communications at 887-2198 with information.
The key to finding Sister Catherine's killer, said Lt. Sam Bowerman, an FBI-trained profiler, "will come from specific, noticeable changes in his behavior and things he said about the case to friends and family."
"The question now is: Can those changes that took place then be recalled by those closest to him after all these years, and are they willing to come forward?" the lieutenant said.
Lieutenant Bowerman said he analyzed what is known of the case and concluded that the killer:
* Was probably between 18 and 27 in 1970, with a record of petty theft, minor assault and drug or alcohol abuse.
* Was unable to get along well with others, was probably a loner who worked part time and was dependent on others for subsistence.
* Probably lived with an older relative who paid the rent in the vicinity of the Carriage House Apartments in Southwest Baltimore, where Sister Catherine lived.
* Knew well the area around the Carriage House Apartments and around the site off Monumental Avenue where her body was found.
* Did not plan the crime or know his victim was a nun, though their paths might have crossed previously in the community.
* Probably knocked out Sister Catherine, possibly by choking her, judging by marks on her neck, then assaulted her, killed her and dumped her body in Lansdowne.
* Showed no guilt or remorse until years afterward. The killer's primary concern was whether he would be caught.
Lieutenant Bowerman said that any personality changes in the killer would relate directly to the slaying, and that the killer's curiosity would have led him to talk about the case at times over the years.
"His life was never the same after Friday, Nov. 7, 1969," when Sister Catherine was abducted and killed, Lieutenant Bowerman said.
The critical periods would have occurred when the killer was under the greatest stress -- the night the nun disappeared and the day her body was found. Friends and relatives would have noticed changes in behavior at those times, Lieutenant Bowerman said.
Most noticeably, the killer probably would have tried to leave the area, perhaps using the excuse of looking for a new job. Or he might have said he had to leave for health reasons or to visit relatives in another state, he said.
Killers often exhibit extreme changes in behavior. For example, a nonreligious person might suddenly begin attending church, or an occasional alcohol or drug user might increase his use or abandon it altogether, the lieutenant said.
Other tip-offs could have been obvious changes in eating and sleeping habits or personal appearance, such as growing a beard or getting a haircut.
"We'd be interested in talking to anyone who has discussed the murder of Sister Catherine Ann Cesnik in any manner over the past 24 1/2 years," Lieutenant Bowerman said.