Unlike manual techniques, a 3D laser scanner captures millions of data points to create a point cloud map. Multiple 360-degree scans can be combined to create a complete 3D view of a scene that can be revisited later in great detail.
Tape measures and photographs used to be the standard equipment for documenting any type of scene by law enforcement. But uneven ground and poor lighting posed challenges and affected the quality of results. it was also sometimes difficult to know what areas to focus on, and important evidence was often missed. 3D laser scanners don't have the same limitations.
Unlike manual techniques, a 3D laser scanner captures millions of data points to create a point cloud map. Multiple 360-degree scans can be combined to create a complete 3D view of a scene that can be revisited later in great detail. This allows detectives, prosecutors, and juries to see the scene of the crime exactly as it appeared when first captured. It also allows investigators to take precise measurements and examine pieces of evidence they didn't realize were important until after the fact.
"When I first started we used tape measures to establish a base line. Then we used a total station, but it has limitations inside," says Lt. Mike Young of the Kearney (NE) Police Department. Among his other duties, he is an accident and crime scene reconstructionist for his department and a senior member of the Kearney/Buffalo County Fatality Accident Investigation Team. "With the 3D laser scanner, it works amazingly well both inside and outside, and it doesn't matter if it's light or dark," he says.
Scanning Technology
Young and his department use the Faro Focus3D X 330 scanner and Faro Scene software to process the scans. Then they use Faro Reality software to create animation in 3D. Faro Reality can also be used for 2D and point cloud environment animation. All of these can be combined to create diagrams and presentations for court.
"You're working with a vast amount of data, 9,000 points per second," says Young. "And it can all be in color. You choose which. You can scan in complete darkness, but if you have daylight or lights on in a residence, it will scan in full, vivid colors just like you're standing there."
When assisting a fire marshal investigating a fatal house fire, Young's scan of the scene was more useful than the photos that were taken. "A fire scene soaks up so much of the light with photography. But the scanner got amazing 3D of the entire residence," Young says. It even showed the charring on the ceiling, which helped them pinpoint an area of focus for the origin of the fire.
CSI Karen Livengood of the Orlando (FL) Police Department Crime Scene Unit uses a Leica ScanStation 3D laser scanner for homicides, traffic homicides, shootings, and police use-of-force incidents. The unit also uses the technology to aid local crime scene units in investigating any homicides that occur in 12 neighboring cities that are part of the local Joint Homicide Investigative Team, or J.H.I.T.
The Leica ScanStation series includes three scanner models, the P40, P30, and P16, that all work with the company's 3D point cloud software suite, which includes of Leica Cyclone stand-alone software, Leica CloudWorx plug-in tools for CAD systems, and the free Leica TruView that allows easy sharing with those who don't have sophisticated viewing software.
"Our scan data has been introduced and accepted as scientific evidence on two of our court cases," Livengood says. "But it has been brought up several times in depositions. The state attorneys have requested copies on several cases, including officer-involved shootings and a number of homicides, that are coming up for court."
Devil's in the Details
As already mentioned, a 3D scanner captures millions of points so that details of the scene captured in time can be viewed later. "The scanner captures everything on the scene. That ability, to me, is what makes the scanner worth it," says Livengood, who often gets requests from detectives for additional measurements.
"The closer you are, the more detailed you get," says Young. So if you know there is a specific detail you want to get, such as an entry wound on a body, you can get close to it when you do a scan for a better view later. Livengood was documenting a homicide scene where the victim had been stabbed multiple times in a living room and it was important to capture scans of all of the blood that was on the ground and everywhere else. "We had one ScanStation scanning at ground level, and another was simultaneously scanning on a tripod. Then we merged the scans together," she says.
Presenting in Court
But if there is a detail you didn't know to look for originally, if a 3D scanner was used at the scene that detail will still have been captured and you will be able to view it. This can be especially useful in court.
"It takes the judge or jury and puts them at the scene when it was committed," says Young. Although the case didn't end up going to court, Young and his team were able to recreate the views of different witnesses in a bank robbery to help test whether their statements were accurate, based on where they were located when the incident occurred.
"At a bank, you have a lot of offices, and all witnesses have a different perspective based on where they were when the robbers came in," says Young. "In court, they can say I was here when they did this, and this is what I saw. A year down the road when the case goes to court, things may change, memory may change, but [in our 3D views] everything is exactly as it was at the time we scanned it."
In addition to her agency's scan data being accepted as evidence in court, the resulting imagery from Orlando PD's Leica ScanStation has been extremely useful in cases, Livengood says. "Presentation in court has just been phenomenal, especially when it comes to bullet trajectories or skid marks for traffic homicides," she says. "The data gets shown to defense attorneys, and they show it to clients. Sometimes, it changes the outcome of the case. If you can see it, to me, that right there pays for itself."
Fast and Efficient
Beyond all of the benefits of 3D laser scanning technology for investigations, the equipment allows officers to fully document a scene with fewer people and in less time than before, no matter the conditions.
What used to take at least four people hours to complete can now be done in a fraction of the time by one person, Young says, although he prefers to use two officers. The setup is simpler and faster, and because of this many more areas can be covered, even if there are special requests for detailed scans. "It takes less than 10 minutes from the time I arrive on scene to the time I'm actually collecting data," says Young. Scans are taken before anyone else touches the scene to best preserve the evidence. This took some getting used to and changes to protocol, but it's worth it, he says. And he's done so quickly, compared to before, that the other officers can then do what they need to do without much delay.
Both Young and Livengood deeply appreciate their 3D laser scanners and agree that it's worth changing some policies and spending time and money on the equipment and initial training for a more accurate and efficient way of documenting crime scenes.
