How Virtual Crime Scenes Work

Virtual Crime Scene Graphics

Many VR rendering programs start with a two-dimensional set of blueprints or sketches like this one.
Many VR rendering programs start with a two-dimensional set of blueprints or sketches like this one.

The first virtual crime scenes were created in computer models. Investigators took careful measurements at a crime scene, including the dimensions of the scene itself and the relationship between all the objects inside the scene. For example, at a murder scene in a house, an investigator measured the dimensions of the room, the position of the body and the location of any other related information, like weapons or blood. Often, investigators used laser distance meters or a total station (a surveyor's tool) to ensure accurate measurements. Crime photographers took pictures of the scene from multiple angles. After the initial crime scene investigation, the investigator returned to the police station.

At the station, a computer operator took the measurements gathered by the investigators and entered them into a computer program. The program then rendered a three-dimensional space using that information.

Some programs required human intervention to make the spaces accurate -- one particular approach required a programmer to adjust the height of a room manually. The programmer used a Computer Assisted Design (CAD) program to adjust the computer model, create furniture or insert the figure of a body. Some early programs also included a library of common objects, like file cabinets or desks, to make the process a little faster and, therefore, less expensive.

Time and money were the two biggest obstacles to making virtual crime scenes a useful tool. The early programs needed a highly skilled computer programmer or graphics designer to make the environments convincing enough to be useful and immersive -- in other words, they didn't give the viewer a sense of presence within the virtual scene. Police forces needed software that had a much less steep learning curve and automated as much of the process as possible.

Today, several software companies offer products that automatically build rooms based on either basic measurements or a two-dimensional room plan. Most of these programs also include extensive object and texture (overlay graphic) libraries, allowing the user to customize the virtual environment and make it as accurate a representation of the real crime scene as possible. Most of these programs can even include the flight path of a bullet (as previously determined by investigators using standard forensics techniques).

TV series like “Bones” often exaggerate what VR systems can do. TV series like “Bones” often exaggerate what VR systems can do.
TV series like “Bones” often exaggerate what VR systems can do.
Photo courtesy

The advantage to the improved virtual environment is that once it's rendered, users can now view the scene from any angle, including from vantage points that are difficult to access in the real world. By looking at the scene from different perspectives, investigators have more information that can help them accurately determine the course of events at a crime scene. Some programs also allow a user to add in animations, allowing investigators to view their theories in action.

If the program supports video output like a head-mounted display, the user can experience a strong sense of immersion, which can help witnesses recall more details or allow investigators to check lines of sight.

But modern virtually rendered environments have disadvantages. The biggest disadvantage is the need for an employee who has enough technical savvy to work with the program -- even with programs that automatically build environments, a user often has to make adjustments. Another disadvantage is that virtual environments are rarely perfect copies of the real crime scene. As a result, investigators or witnesses may become distracted by the imperfect simulation and miss important details.

In the next section, we'll look at a different method of constructing a virtual crime scene.