It's a given that criminals such as arsonists and serial murderers often return to the scene of the crime -- sometimes to relive the crime. But not only criminals do so.
Detectives, prosecutors and juries must also revisit the crime scene. Detectives may need to re-examine the evidence, prosecutors may return for case preparation and jury members may need to review the crime scene to make a decision.
To do their re-evaluations, investigators typically rely on photographic evidence and two-dimensional drawings. Since we live in a three-dimensional world, however, it can be difficult to visualize the positional relationships of evidence with two-dimensional tools.
What if agents could measure with extreme accuracy thousands of data points per second in a crime scene? What if an agent could capture that information, recall it and create his or her own virtual representation for use during a trial?
Through a combination of laser and computer technology, high-definition surveying (HDS) creates a virtual crime scene that allows investigators to maneuver every piece of evidence.
HDS reflects a laser light off of objects in the crime scene and back to a digital sensor, creating three-dimensional spatial coordinates that are calculated and stored using algebraic equations, said Tony Grissim, homeland security and law enforcement liaison for Leica Geosystems HDS, based in San Ramon, Calif.
"An HDS device projects light in the form of a laser in a 360 degree horizontal circumference," he said "The HDS is measuring millions of points, creating a 'point cloud.'"
Think of letting off an insect bomb in your apartment -- millions of particles create a fog, and the resulting cloud settles on all objects in your apartment. With HDS, instead of millions of data particles settling on the objects, those data points are bounced back to the receiver, collected, converted and used to create a virtual image of any location.
An average desktop personal computer can now take the data file and project that site onto your screen. Not only has the scene been preserved exactly, but the perspective can also be manipulated. For instance, if the crime scene were the front room of an apartment, the three-dimensional image allows the investigator to move around and examine different points of view.
Or perhaps the victim was found seated. An investigator could see and show a jury what the victim might have seen. If witnesses outside said they looked in a living room window, an investigator could zoom around and view what the witnesses could or could not have seen through that window.
Cloud of Information
"Understanding evidence documented on a 2-D drawing of a staircase is difficult," said Derry Long of Plowman Craven & Associates (PCA), a land surveying company based in the United Kingdom. "If you create a 3-D staircase and cut-away, the relevance of evidence is often clear."
Long spent 12 years as a civilian employee of Scotland Yard, where he designed police stations and developed computer modeling. At PCA, he uses HDS to re-create crime scenes down to the submillimeter level. Although PCA's focus is working with builders and developers, Long created the first HDS call-out team in Europe for criminal investigations.
His team, on-call 365 days a year, responds to about 150 incidents each year.
Many times, Long responds to a scene weeks after crime-scene investigations are concluded. His job, then, is to scan the scene, and then use the photographic documentation and crime-scene notes to re-create the scene.
Long recalled a recent homicide where the murder was thought to have occurred in the kitchen, but no one could determine how the body ended up in a hallway. By re-creating and studying the crime scene, investigators examined different points of view and the positional relationships of the evidence.
"Now it made sense, the investigators were able to see what had happened," said Long, adding that because the case is still ongoing he can't provide further details.
Keeping the Scene Clean
A basic concept taught to first responders is securing a crime scene, so contamination of evidence is minimized.
Crime-scene contamination can take many forms -- someone may touch an object leaving their fingerprints, or inadvertently move or take evidence from the scene, perhaps by picking up fibers on their shoes.
Analyzing a scene's evidence helps explain what happened, and if an item of evidence is moved or disturbed from its resting place, the analysis could be faulty.
The time after a crime has been committed, during which there is a maximum potential for the recovery of forensic evidence, is referred to as "the golden hour" by Mark Harrison, MBE, special adviser to the UK's National Crime & Operations Faculty (NCOF).
Harrison, an 18-year veteran of British policing, is on loan from the Bedfordshire Police to the NCOF, a national organization in the UK that provides special services during complex investigations.
He commonly uses HDS technology as a "stand off" device, allowing him to approach the scene in stages by scanning from the outer perimeter and moving into the heart of the scene.
"The laser doesn't care if its day or night," Harrison said. "It captures the information and allows me to interrogate the crime scene with my laptop before it has been disturbed."
In the past, the method of preserving information about the evidence was photographic documentation and two-dimensional drawings. Later, not only could someone testify to the recovery of the evidence, they might also provide expert interpretation. Drawings and photographs assist investigators in the investigation, and ultimately assist prosecutors in telling the story to a jury.
In many cases, Harrison said, the value of evidence is in its positional relationship.
"It could be blood splatters, a firearm, shell casings or any other pieces of physical evidence," he said.
Investigators often go to elaborate means to reconstruct scenes. Unfortunately no matter how good your photographer, there is always something else an investigator wants to know. Photographs and drawings are helpful, but they are two-dimensional, and are the technician's interpretation of the scene.
Long and Harrison agree that observer bias always creeps into photography and crime-scene drawing. If an HDS device is used at the scene, detectives, prosecutors and juries can return to a crime scene in its preserved state.
Matter of Perspective
The investigative and prosecutorial value of virtual crime scenes is evident. Showing a jury exactly what a witness could or could not have seen can be very valuable.
Recently Craig Fries, president and founder of Precision Simulation, said his company was asked to re-create an officer-involved shooting in the San Francisco area that occurred one year earlier.
There were more than 40 witnesses to the incident, he said, and the scene itself was approximately 400 feet by 2,000 feet -- an entire city block with businesses and apartments. Using HDS technology, Fries scanned the scene, the involved vehicles (at the impound yard) and used photographic evidence to reconstruct a virtual model of the incident that could be examined from almost any point of view.
"Once the plaintiff knew what we were able to provide, they dropped the lawsuit," Fries said, adding that HDS technology is beginning to be a tool used by both the defendant and plaintiff. "If done well, it's very compelling to the jury."
HDS works equally well in a large rural area. Harrison recalled a political execution in Ireland where the crime scene was a large pasture. HDS technology allowed investigators to document the entire scene in a relatively short period of time and was extraordinarily useful in their investigation.
Long and Harrison also said UK agencies have scanned vehicles, train crashes, river crossings, buildings and planes. From the point-cloud data, investigators in the UK can develop two-dimensional line drawings, three-dimensional models, animations and interactive multimedia packages.
The system also has training applications. Currently there are driving, pursuit and use-of-force simulators. Using HDS, police officers could be taken into a virtual world to practice their skills, or taken back to actual events and debriefed on their own or other police officers' actions.
HDS technology could be used for tabletop exercise, and in addition to training, the technology has a real-time application in tactical situations. Harrison explained that if there were a hostage situation on an aircraft, a similar aircraft could be used to create a virtual representation of the problem.
"Within about two minutes, you could scan the interior of the second aircraft, upload the data and hand virtual goggles to the tactical team," he said. With that data, combined with other real-time intelligence, the team could explore the interior of the aircraft before taking action.
In the UK, government agencies are beginning to use HDS to document critical infrastructure as a means of furthering emergency planning. It would be valuable for fire, and emergency medical or tactical teams to have access to virtual information about buildings.
Imagine a tactical team virtually touring the inside of a school where children are being held hostage. As with the aircraft scenario, the HDS could produce a virtual school, and combined with real-time information, could give tactical teams an edge over the hostage-takers.
For this to be effective, though, the HDS scanning of critical structures must take place before the incident. As we go forward in the 21st century, we will likely see this technology take an important role in criminal investigations, civil liability, training and emergency preparedness.