Documentação de cena de homicídio com scanner a laser 3D

Kansas crime lab’s trial test of new Leica Geosystems 3D laser scanner at a homicide scene provides a powerful demonstration of the forensic tool’s superiority over traditional methods of crime scene mapping.

On Easter Sunday 2010, police detectives responding to a homicide within the Kansas City metropolitan area requested the Johnson County Criminalistics Lab to dispatch its crime scene investigation unit. For Ryan Rezzelle, supervisor of the lab’s five crime scene investigators, the call represented an unexpected opportunity. Just two days earlier, Rezzelle had received on loan from Leica Geosystems the newest model ScanStation C10 3D Laser Scanner which he and his team had been testing as a forensic instrument for crime scene mapping.

“I thought, ‘What better way to compare the ScanStation’s capabilities with our current mapping methodologies than to use it at an actual crime scene,” Rezelle said. “We could piggyback the scan data collection without any intrusion. That would provide a real-time field trial test and a side-byside comparison with the protocols used and evidentiary data obtained by the police traffic accident investigation teams that are currently called upon to do the measurements.”

That the Johnson County Criminalistic Lab was considering cutting edge forensic measurement technology is not surprising. The lab, administered by the Sheriff’s Office, serves a population of over 560,000 residents in both the rural and urban areas on the Kansas side of the greater Kansas City metropolitan area, and has a reputation as one of the most progressive, well-equipped high tech crime labs in the country. Both Sheriff Frank Denning, long a believer in the value of highly professional forensic services, and the lab’s director, Gary Howell, were strong proponents behind the recent commencement of construction planning on a state-ofthe-art crime lab, slated to open in early 2012 in Olathe, Kansas.

In addition, the lab is accredited by the American Society of Crime Laboratory Directors Laboratory Accreditation Board under the ASCLD/LAB International Program, a comprehensive accreditation that has been earned by only about five percent of the crime labs in the U.S.

After obtaining permission from the lab’s quality assurance manager to trial the ScanStation, Rezzelle and his team investigated the crime scene, the focus of which was the body of a man shot to death in the front seat of a car. Mounting the scanner on its tripod, the investigators conducted three exterior scans within 45 minutes, along with the associated digital photographs. “The set-up and scanning was fast and easy,” Rezzelle said. “We had learned the procedure in about half an hour on Friday with the Leica representative remotely talking us through the process on a speaker phone.”

After the body of the victim had been taken from the car, the team removed the scanner from its tripod and placed the unit on a special Leica accessory mount on the car’s center console armrest and captured a 360 degree scan of the car’s bloody interior. A second 360 scan was conducted from the rear seat for a total of five scans.

“What amazed us was, from set up to the time we put the scanner away, we were there maybe sixty to ninety minutes, tops,” Rezzelle recalled. “Compare that to the traffic accident unit, a two man crew using a total station and prism poles, along with their tape measures, hand-held laser distance measuring tools, and Rolatapes, who worked for eight to ten hours marking and measuring single points. We had captured the same scene with literally millions of points in a fraction of that time.”

Late the following day Rezzelle overnighted the laser scanner to Leica Geosystems’s Georgia headquarters, following which a technician there quickly processed the five scans and “stitched” them into a single “point cloud.” Two high-value exhibits were then generated from the data consisting of a 3D fly-through of the crime scene and a Leica TruView. (Leica TruView is a free plug-in for Internet Explorer which allows CSIs to quickly and easily share scene data with command staff, detectives and prosecutors. TruView was recently used in a Georgia homicide trial to virtually place the jury at a crime scene.)

For agencies that have purchased a Leica 3D laser scanner, this procedure is performed by in-house personnel who have completed a police oriented training regimen developed by Leica Geosystems. In all, the process took five to six hours, the great majority of which was computer “rendering” and processing time. By Friday morning the results were in Rezzelle’s hands.

“We were blown away. So was every one who saw it,” Rezzelle said. “We had captured some fantastic data from the car’s interior, and by stitching together all five of the scans we had a mountain of useable evidence. Sheriff Frank Denning was especially impressed by the fly-through animation. Personally, it’s one of the most impressive presentations of a crime scene that I’ve seen in many years. So, even though we regarded ours as a rushed first-effort test, we produced something that could be viewed by prosecutors, CSIs, attorneys, and crime scene reconstructionists as stellar output for getting a good clean crisp perspective of the relationship of different components at a crime scene.”

Three dimensional laser scanning has recently taken on additional importance in criminology in the wake of the 2009 report by the National Research Council (NRC), a committee of the National Academy of Sciences (NAS). Titled “Identifying the Needs of the Forensic Science Community,” the report focuses on strengthening the current benchmark standard published by the International Organization for Standardization (ISO), commonly called the ISO 17025. Historically, crime scene response units in most U.S. police agencies have been routinely exempted by their management from the requirement to become accredited. That attitude is changing fast as a growing number of agencies seek accreditation for their crime scene units in a tacit acknowledgment that ISO 17025 protocols should begin at the crime scene and not wait until the evidence reaches the crime laboratory.

Rezzelle is convinced the Leica Geosystems ScanStation C10 laser scanner will have an essential role to play: “I think this is what the NAS will want. Once people see the output that’s available from the C10, there will be an expectation that this will be used to capture every crime scene in the United States. They [the NAS] are calling for forensic science to be based on science, and that’s what we have here. It’s telling. It’s descriptive in terms of what you’re seeing visually. This is going to be the next generation of mapping for crime scenes.”

Written by Tony Grissim