Crime scene

reconstruction

has become

simpler and

more accurate,

thanks to low

cost, user-friendly

3-D CAD software.

The man claimed he was acting in self-defense. When an intruder suddenly entered his motel room, the victim said he had no choice but to strike the man with a lamp, knocking him unconscious.

But the evidence told a different story. Using drawings created by a three-dimensional computer-aided drafting (CAD) program, the police were able to show that the intruder was actually well inside the room and sitting in a chair when he was struck, not at the door as the alleged victim claimed.

By carefully measuring the angle at which blood spots hit the motel wall and floor, the police were able to reconstruct exactly where the accused was situated when he was hit. What had looked like an act of self-defense against an attack now appeared to be an ambush.

According to Paul Breuninger, a police investigator and 25-year veteran with the Cook County Police Department, witness testimony is always the weakest link in any investigation. Hence the need to corroborate or refute witness statements using physical evidence. "With CAD you can create an actual model of the crime scene and view it from any angle," he said. "It allows you to view just what the witness says he saw."

For years, police have done crime reconstruction using tape measurements and, in the case of blood spatter analysis, pieces of string. Then the information had to be carefully drawn to scale -- a task that was extremely time-consuming.

Since 1985, Breuninger has been using CAD software to do the work for him. Unable to afford costly CAD software at first, Breuninger wrote his own program. Later, he bought one of the early 3-D CAD programs. Today, 3-D CAD software can be purchased for hundreds of dollars instead of the thousands it cost a few years ago.

Breuninger works with a product called DataCAD, a $300 architectural program produced by CadKey Inc. Easy to use, DataCAD needs just two points from which it can render a wall versus the 16 lines required by other 3-D CAD programs. Doors, windows and other architectural elements can be easily added and all drawn to exact scale, according to Breuninger.

From science to law enforcement, 3-D drawings are valued for their ability to portray information in an understandable way. Whether it's viewing a 3-D model of a DNA molecule or a crime scene, the mind absorbs information displayed in three dimensions like a sponge. By working in three dimensions, CAD users can create scenes that can be viewed from any angle. Suddenly, very technical evidence can be visualized by nontechnical people. Juries can "view" crime scenes and see the location of evidence. They can view what a witness claims to have seen or not seen. And as Breuninger pointed out, "evidence doesn't lie."

Breuninger recalled a case in which a man told authorities he had not seen a murder that occurred in his kitchen. He claimed he was in the attached garage at the time, and the kitchen was not in his line of sight. By re-creating an accurate model of the man's house, Breuninger depicted the view from the garage toward the kitchen, verifying it was actually possible to observe something happening inside the kitchen. From the reconstruction, authorities were able to determine that the man could have seen the murder.

A PRECISION TOOL

So why use CAD and not one of those popular graphics drawing programs to reconstruct crime scenes? According to Breuninger, the reason is precision. "You tell CAD the exact dimension and you get a scaled drawing," he said. For people who use CorelDraw and other drawing software, accuracy is not an issue. As a