When Accuracy Matters, Validation Is Crucial

When the Crime Scene Investigation Section of the Johnson County Sheriff’s Office Criminalistics Laboratory in Olathe, Kan., took delivery of its new Leica ScanStation, the CSIs were not permitted to deploy the high-definition 3D laser scanner as the sole means for documenting casework until its accuracy was validated. “When we get any sensitive instrument for use in the crime laboratory, it goes through scientific validation,” said CSI Section Supervisor Ryan Rezzelle. “Our C10* went through that.” 
calibration_croppedEach and every Leica ScanStation undergoes rigorous calibration and quality assurance tests before leaving the manufacturer. The ScanStation also contains an internal calibration system that prevents activation if unsuccessful. However, as an ASCLD/LAB-International-accredited laboratory, it was important to scientifically test and verify the scanner’s accuracy independently. “If questioned about our process,” Rezzelle said, “we can say that, beyond being told by somebody that it is valid information, we verified it by applying a scientific testing process to make sure that, by our standards, we also believed that it is a valid tool for measuring spaces.”

The Validation Process

Rezzelle and his CSIs received 32 hours of public safety training from Leica in February 2011 and spent the next month honing their skills. Then the validation period began. From mid-March to mid-June, the team used the scanner in tandem with traditional data-collection devices, including a total station and NIST-certified tapes, for practice and comparison and to validate the data with Leica Cyclone point cloud processing software. “We validated our scanner to hundreds of measurements that we collected from a variety of scenarios—inside and outside in varying light—looking at the measurement of angles, registering scans together, and ensuring that the measurements that we collected from registered scan data were still sound,” Rezzelle said.
Once the process was complete and documented, Rezzelle appeared before the laboratory validation committee. “They had to meet,” he said, “review my documents, and basically establish that my process was sound.” In July 2011, the validation process was affirmed and the scanner approved for use. “The fact that there was a learning curve with this one added to that length of time from the day that we received it until the day it could be used,” Rezzelle said. “If we were to upgrade tomorrow to the PS20, I could probably complete a validation on it now in about a week or two.”

Independent Validation Stands up in Court

Even though this initial laser scanner validation period took several weeks, it was not an excessive exercise or a waste of time. It was necessary to establish that the ScanStation delivers not only impressive visualizations but also highly accurate and verifiable data. “We can say that it is scientific—not just a fancy thing that tells us neat stuff and gives us a cool picture to look at,” Rezzelle said. “We’re actually looking at scientifically valid data.”
This is especially important in the courtroom when facing jurors who are unfamiliar with the technology or, more importantly, a Daubert challenge. Forensic science is an objective discipline, Rezzelle explains, and the job of a CSI is to present fact. Nevertheless, when testifying in court, CSIs occasionally face opposing counsel and defense experts who attempt to deconstruct their work. “If we have a scientifically validated work product,” Rezzelle said, “it becomes more difficult to pick apart the work that we’ve done, and our objectivity stands just a bit more firm.”
* The C10 is equivalent to the PS10.
For more information about high-definition 3D laser scanning solutions for law enforcement and crime scene investigation, please contact us.
To download a report on Leica ScanStation calibration and quality assurance measures, click here.
About the author: Wendy Lyons is journalist living in Canton, Georgia, who spent several years writing about surveying technology for POB magazine. She now focuses on covering laser scanning and other geospatial measurement solutions for public safety professionals.
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