ForensicsCollaboration with industry leads to improved forensics
Three-dimensional (3D) scanners used at crime scenes for forensic investigations are not just the stuff of prime time television. Investigators and crime laboratories are using 3D laser scanning measurement systems to measure and model, in 3D simulations, the critical aspects of crime scenes. A 2009 National Academy of Sciences (NAS) report, however, questioned the reliability of some forensic sciences, including the use of 3D scanning technique. Furthermore, pressure began building in the forensics community to have crime laboratories and stand-alone crime scene units in the United States adhere to specific standards in their services, which require traceability to the SI [the SI in SI traceability refers to the International System of Units (Système International d’unités)].
Three-dimensional (3D) scanners used at crime scenes for forensic investigations are not just the stuff of prime time television. Investigators and crime laboratories are using 3D laser scanning measurement systems to measure and model, in 3D simulations, the critical aspects of crime scenes.
A NIST release reports that a 3D laser scanning measurement system has a motorized swiveling head that sweeps a 632 nm wavelength laser beam over an entire room or outdoor scene, capturing up to a million measurements per second. A panoramic image is output with a 3D data visualization that reproduces the dimensions of the area. These data are then used to identify bullet trajectories, victim positioning and orientation, witness viewpoints, etc., with high accuracy and speed.
In the typical use of a 3D scanner, investigators will position a length artifact in the scene to be scanned along with everything else. The length of the artifact is a known value, and the measured value is compared with the known value in the field to test if the instrument is working correctly before critical measurements are performed.
“They take a complete 3D scan so that later they can go back and query this data to see, for example, how far this wall is from where this person is standing over here,” describes Christopher Blackburn, a key member of the PML team involved in dimensional measurements.
“There are points in space, and each point is an X, Y, Z coordinate. So you can query the distance from any combination of different points. You have the whole thing captured.”
Without established length standards to assess the scanner performance, the investigators may not be able to defend the method as having an acceptably high level of certainty and the results might not be admissible in court.
The 2009 National Academy of Sciences (NAS) report Strengthening Forensic Science in the United States: A Path Forward questioned the reliability of some forensic sciences including the use of this 3D scanning technique. Furthermore, pressure began building in the forensics community to have crime laboratories and stand-alone crime scene units in the United States adhere to specific standards in their services, which require traceability to the SI [the SI in SI traceability refers to the International System of Units (Système International d’unités)].
