As 3D scanners become more common for capturing and preserving evidence, police, forensic technicians, attorneys, and others involved in the legal industry need to be aware of the applications, benefits, and limitations of how this technology is applied in recording data and subsequently how it can be used to aid in the analysis of evidence and crime scenes. The following article provides an introduction into the ever growing application of 3D scanners in the forensics industry.
The start of any forensic investigation must begin with the collection, review, and analysis of evidence. As a general rule of thumb, the better the quality of evidence, the better the analysis and likelihood of solving the crime. This is why there is a regular stream of new products, equipment, and software to aid the forensic technician in the collection, organization, and analysis of evidence. Many products or technologies are specialized in the collection of evidence while others' sole purpose is to keep evidence organized. However, even fewer technologies can collect, organize, and provide the analysis tools all in one package. This is the main reason why 3D scanning for forensics is an ever growing and useful application of laser based measurement technologies in fighting crimes and reconstructing events.
Often referred to as High Definition Surveying (HDS), 3D scanning became popular in the late 1990s for surveying buildings, terrain, and other architectural features in a very rapid and detailed manner. However, it wasn't long before many in the industry realized that the quick capture of vast amounts of point data was invaluable over the more traditional total stations. 3D Scanners can obtain tens of thousands of point measurements per second, while most total stations capture one measurement every few seconds (at best). Therefore, the time savings and possibilities available with a 3D scanner would be practically impossible with more traditional methods. The end result is that accident and crime scenes can be released in a fraction of the time with more measurements than were ever possible before.
The term "3D Scanners" makes up a broad range of devices and technologies all aimed at taking a large quantity of measurements of an object's surface or environment. The choice and application of 3D scanning often depends on the size of the object (or environment) being scanned along with an understanding of what will be done with the data once it is captured. These two factors often drive the type of technology that can be used to obtain measurements and in some cases, what type of software will be used to edit the data.
Some scanning technologies are based on optical methods whereby photographs are used to collect and match points in corresponding photographs (i.e. Photogrammetry and stereo matching) while the lesser known CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) allow the interior structures of objects to be "scanned" and examined. The more common 3D Lidar (Light Detection and Ranging) scanners emit a beam of light and measure the part of the beam that is reflected back to the instrument. These are the most common types of scanners—often featured on "CSI" type shows as being able to collect and preserve data from very large crime scenes.