Forensic Surveys Help Accident Investigation
For those who perform crash and crime scene reconstruction work, the goals are clear: collect evidence, tell an accurate story of the scene and present a good case for justice. While the objectives are straightforward, getting there is far from it. Crime scene forensics investigators and accident reconstruction specialists are charged with documenting scenes and collecting evidence for scientific analysis in challenging environments that require them to work quickly.
Historically, accident reconstruction teams have collected and marked evidence, such as tire marks, and applied math to estimate speeds before a collision using a combination of critical speed formulas, tire radius values, the coefficient of friction and road elevations. As geospatial technology has advanced in recent years, the forensics investigator’s toolbox has grown to include drones or unmanned aerial vehicles (UAVs), photogrammetric analysis, total stations, and more recently, 3D laser scanners.
Total Stations as Forensics Workhorse
A foundational tool for professional surveyors, the total station is now used in crime scene investigations or crash reconstructions to calculate the horizontal distance and angles to specific points in 3D and accurately perform surveys. With total stations, teams use measurement data to build vehicle damage profiles and capture specific locations of evidence and terrain.
Ryan Zukowski, a state trooper for 22 years and part of the Wisconsin State Patrol Technical Reconstruction Unit, explains that his team uses several geospatial products to collect forensic data at crime and crash sites. These include Trimble S6 total stations and R10 integrated GNSS systems.
Zukowski also runs his own private crash reconstruction business called Capital Crash Analysis where he rents and uses Trimble geospatial products from Seiler Instrument throughout the Midwest. He’s consulted on more than 1,000 traffic crashes and has technical expertise in numerous disciplines such as speed analysis, occupant kinematics, pedestrian crashes, time-distance relationships, photogrammetry, crash data retrieval and more.
“The technology for law enforcement continues to evolve and create better opportunities for getting justice more quickly,” Zukowski says. “You can’t argue with data and technologies that are proven to be so accurate. As tools diversify, getting data from two different kinds of tools in one helps us present the facts of the case in a more complete way.”
Laser Scanning Preserves Evidence
Newer to the forensics field is 3D laser scanning technology. These tools allow analysts to collect precise dimensions, evidence and features to be recorded for later analysis. By capturing large amounts of data very quickly, 3D laser scanners allow investigators to capture a complete 360-degree image of a scene in minutes. The Trimble TX8 3D laser scanner, for example, captures up to 1 million points per second and can perform a typical high-density scan in about three minutes.
“In a traditional crime scene, investigators identify all the evidence in the environment,” Zukowski says. “Some evidence is tangible such as a gun or a knife, while other evidence is residual, like blood, fluid and footprints. The challenge is you don’t always know the value of what’s on your scene until later. With 3D laser scanners, you are measuring and documenting absolutely everything, so your entire scene is preserved exactly as it was.”
Scanning variables include the density settings of the scanner and the distance from the item. A small drop of blood on a wall may or may not have a scan point depending on these variables. “If documenting them precisely is important, then the technician will make sure the density settings are high and the area is scanned from different positions/angles,” Zukowski explains. “Also, scanners use cameras to colorize scans when light is available, but light is not required to scan items.”
Part of the value of bringing 3D scanning to crime and crash investigations is the fact that evidence can be documented, analyzed and processed later, as needed, enabling investigators to more quickly clear the scene. This might happen if new evidence surfaces or if suspects change their stories.
Until recently, 3D scanners had been slow to be adopted by forensics teams, mostly because resources are tight for law enforcement agencies and many already invested in their total stations, according to Zukowski. The Wisconsin State Patrol Technical Reconstruction Unit, for instance, currently provides forensics mapping expertise to 72 counties across the state with 17 robotic total stations, six GNSS rovers, and only three 3D laser scanners. That means Zukowski and his team must shuffle laser scanning equipment and manpower across the state at a moment’s notice.
Complete Scene Capture
A new hybrid tool may change forensics investigation workflows yet again. It is an integrated 3D scanner and high-accuracy total station-in-one – the core of the Trimble Forensics SX10 Solution, which includes a robotic total station, 3D laser scanner, cameras, Trimble T10 tablet for data collection and Trimble Forensics Capture field software specifically designed for forensics data collection. The solution captures high-accuracy total station measurements, photographs and high-accuracy 3D laser scans. By capturing three data types in one project file, users can select the right tool for the job at the moment it is needed. Scene data collected can then be exported to a variety of special reconstruction, forensics, and GIS applications for analysis, surveying, dimensional analysis, modeling and visualization. The combining of data from multiple different sensor types or technologies into one solution, called “sensor fusion,” can generate more useful data from missions, which can improve productivity and expand services.
Zukowski sees this hybrid technology as having the potential to make a big impact for law enforcement in time and resource savings. He used the Trimble SX10 scanning total station on a private reconstruction case in rural Iowa earlier this year. Traditional laser scanners require natural or artificial targets – sometimes challenging and cumbersome in rural environments – to assist in project registration in order to tie multiple scans together in a single scene. The SX10 allows users to set and scan from control points throughout the scene, eliminating the need for target-based registration back at the office. With only blowing corn surrounding the crash scene in Iowa, the SX10 allowed for efficient scene documentation in extreme temperatures with wind chills well below zero.
“It used to be that scanning technology was a big leap workflow-wise, getting one data set to communicate with another data set,” Zukowski says. “The path to an end-product, like a forensic diagram or making that data actually useful, has always been clunky. But now with a hybrid option, there’s a doable workflow, so it’s right for a lot of reasons. From a law enforcement perspective, it’s another tool in the toolbox.”
Training is key
Russell Strickland, the crash unit coordinator for the Institute of Police Technology and Management (IPTM), also believes that 3D scanning technology has a place in geospatial forensics. Strickland has been the crash unit coordinator at IPTM since 2014, an instructor since 2004, and a student since 1995 when he was a law enforcement officer himself. IPTM trains some 7,500 students a year, covering everything from crash investigation and reconstruction to criminal investigation, crime scene forensics, crisis/hostage negotiation and several other specialty programs.
IPTM recently announced a partnership with Trimble to provide training for law enforcement and private investigators on Trimble Forensics solutions. Strickland and his colleagues are in the process of learning the SX10 scanning total station, software, and workflows, and will develop complete course material and hands-on training courses on the products, which they expect to offer in the next year.
“The most important thing we look at when we’re training law enforcement is to provide consistent, repeatable and reliable processes for using any kind of technology,” Strickland says. “In law enforcement, there can be a lot of tough scrutiny in how we collect evidence, and when officers get in court, they need to be able to explain how things work in a simple and clear way.”
Strickland believes hybrid forensics technology is valuable because it’s a diverse piece of equipment that works in certain environments where a total station isn’t effective, like when analysts don’t know what evidence is valuable at the scene yet. Plus, it has the potential to help investigators clear scenes more quickly.
“You hear administrators talk a lot about the cost of road closures due to collisions,” Strickland says. “There’s a cost to the community, lost productivity, lost commerce and investigators working. One major incident that closes a highway for three hours can pay for a hybrid system like this.”
Data visualization is also a major component of modern forensics work, and hybrid technologies with better workflows are making it easier. With built-in integrations between the varying geospatial forensics technologies, teams can take evidence and create diagrams, animations and fly-through models that tell an accurate story of the events.
“Part of the work we do with prosecutors is preparing these exhibits for the jury, to help bring them to the scene and to understand what the investigators are talking about,” Zukowski says. “You tell them in words, show them a photograph, and then show them a diagram. These diagrams and models give clarity and understanding to complex expert witness testimony. It’s really helping the jury understand complex opinions – that’s where I see a lot of the value in these exhibits.”