They take ear prints off doors. They lift shoe prints off banana peels. They can tell what someone was hit with simply by looking at the bruise left behind or how long a body has been dead.

They are the nation's top forensic scientists, and many are gathered in Salt Lake City this week.

For the first time, Utah is hosting an "education conference" of specialists from a variety of forensic disciplines.

The conference at the Red Lion is presented by the Utah Division of International Association for Identification and the Northwest Association of Forensic Scientists. Some of the sessions that contain sensitive investigative information are closed to the public.

From Utah, the Destiny Norton murder and the Trolley Square massacre were discussed during a closed door session. Police detectives and experts from the Utah State Crime Lab discussed how evidence was collected and processed during the Norton case, said Utah IAI president and West Jordan police detective Francine Bardole. Those involved with the Trolley shootings discussed how four separate crime scenes all related to the same incident were processed.

Michael Grimm, who worked for nearly four decades with the FBI and Virginia's Department of Forensic Science before recently retiring, said the advancements in forensic technology have led to countless arrests across the country. That's important, he said, because there is no room for error in his line of work.

"We don't make mistakes. If we make mistakes, in most cases it costs us our jobs," he said. "We're not allowed to make mistakes. If we were to falsely identify someone it could mean false imprisonment and, in some cases, death."

Grimm is a skin impression expert. During his "Marks of Madness" presentation Tuesday, he talked about how just about any body part or weapon leaves identifiable impressions.

"Most people think of fingerprints as being the only unique part of the body for leaving impressions," he said. "All body parts are unique. Most of them, however, are left on surfaces not sufficient to recover. Lips and ears are also unique. Even our knuckles are unique."

Grimm received some national attention a few years ago when he was able to help capture a Peeping Tom by lifting the lip impressions the man left on a woman's window. It was a case that even gained attention in Playboy magazine, Grimm recalled.

In another case, Grimm helped bring a man into custody by taking the impression of an ear off a door. The suspect had pressed his ear against a door before breaking in to see if anyone was home, he said.

"It left a very significant impression on the door. There were very minute characteristics on the outer edge of the skin left on the door," he said.