Fourth in a series

When police detectives arrived at the sprawling Fauquier County mansion with reports of a killing, it took them very little time to realize that the story they had heard simply wasn't true. Forensic evidence, police say, doesn't lie.

Prince William police Sgt. Bob Zinn, supervisor of the county's identification bureau, used the 1997 investigation into the death of a polo player on the estate of arms heiress Susan Cummings to illustrate the fact that he can re-create a story with scant physical evidence. Displaying slides depicting blood stains, autopsy photos and pieces of evidence, Zinn explained to the Prince William Citizens Police Academy members that the truth often lies in the minute details.

"We're looking for information that will give us a clue as to who this person is or how they may be linked to the crime," Zinn said. "These crime scenes provide a lot of information about what happened, and after a while you can just look at them and have a good idea about what transpired."

Drops of blood on the floor and "high-velocity impact spatters" on the wall indicated that the man at Cummings's estate had been sitting in a chair when he was shot. A knife lying next to him didn't have any blood on it and appeared to have been placed there after he died, and his mouth was full of food, indicating that he was likely eating breakfast and was caught off-guard.

"Things just didn't add up," Zinn said, recounting Cummings's initial claim that her lover had rushed at her with a knife before she shot him four times. "They knew it just didn't make sense, and they knew it pretty quickly."

Cummings was convicted of voluntary manslaughter in the shooting of Roberto Villegas in May 1998; she served 51 days of a 60-day sentence in the Fauquier County jail.

Zinn's bureau focuses on identifying people and suspects with fingerprint analysis and also runs the county's crime scene unit, which is responsible for gathering forensic evidence out in the field. That evidence, which includes DNA and technical on-scene analysis, is often the crux of a case and frequently leads police to suspects and criminal convictions.

Speaking to the academy during its sixth week, Zinn talked about the science of fingerprinting and the vast network that ultimately links criminals to crimes and crimes to criminals. Zinn said that although it's a highly technical field, much of the work comes down to making sense of a scene and to linking people to it, such as through discovery of useful fingerprint samples.

The identification bureau takes in more than 10,000 fingerprint cards each year, expanding a vast database that can help police solve crimes--including some that haven't been committed yet. For example, if a suspect has left his fingerprints at a scene and is later arrested in connection with another crime, police have an immediate link to the previous crime.

And with the use of DNA evidence, police are better equipped to solve crimes. If a fingerprint isn't available, even the smallest amount of DNA is the next best thing. Zinn said the most important piece of crime analysis is "putting people at the scene."

In some cases, Zinn's work is used to help identify unknown victims or suspects, such as in the recent case of a then-unidentified man who was found dead in a Manassas creek bed. Charlie Hoffman, a Prince William detective who spoke to the academy Wednesday about violent crimes, said that evidence collected in that case led to a positive identification.

Johannes A. DeHart was identified through the use of a tag on his underwear, which led Hoffman's investigation to the Netherlands, where relatives identified the man. Work on the scene determined that DeHart, whose body was dumped in the creek, had been hit over the head with a blunt object.

"Which means there is still a crime scene out there, and we need to find it," Zinn said, adding that there is likely much more evidence that might lead police to DeHart's killer.

Staff writer Josh White is attending the Citizens Police Academy. His reports will appear every other week.