Gathering Evidence Indoors

Crime scenes that are indoors and involve firearms require a special kind of forensics documentation. The necessary technology and attention to detail indicates a growth niche for surveyors.

By Bob Galvin

There are no exact statistics on what the annual percentage of indoor shootings is of all firearm incidents in the United States, but it is significant. The American Firearms Institute, which provides information and statistics about firearms, firearms crime, and gun ownership, reports that nearly 21% of victims of armed violence were involved in some activity at home at the time of the incident. About 25% of all violence by armed offenders occurred at or near the victim’s home.

Such statistics help explain why crime-scene investigators spend a lot of their time investigating indoor shooting scenes. Because cases involving indoor shootings will usually wind up in court, mapping them accurately is pivotal so that jurors will understand a shooting incident’s likely chain of events.

As with any crime scene, shooting scenes (whether indoor or outdoor) must be investigated and documented as soon as possible to preserve evidence. Today’s technology for investigations helps speed evidence documentation. And the tools cover a broad spectrum, including photography, video taping, tape measures, measuring wheels, total stations, laser scanners, data-collection software, and crime-scene-diagramming software, among others. Of course, officer and witness testimony is always provided to support whatever evidence is documented and presented in court. 

Challenges with Evidence

While technology has streamlined documentation of indoor shooting scenes, challenges persist. According to Dave Forystek, newly appointed chief for the Mayville, Illinois, police department and a former investigator for the Flint, Michigan, police department, there can be an overwhelming amount of evidence. More problematic, however, is the disturbance or even destruction of evidence before mapping can occur. “Let’s say you have a small- to medium-sized nightclub with a 3,000- to 4,000-square-foot area, and there was some kind of shooting assault,” Forystek said. “You could have several hundred people here, and as this assault happens everyone’s trying to get to the doors to get out. Evidence is being disturbed [such as a pool of blood or a body], whereas if the scene is outdoors everyone can just run in a shotgun pattern away from what’s happening.”

Another challenge for documenting indoor shooting scenes is that a scene may have had prior incidents. “The structure has been there a long time, and suspected evidence at that scene may not be for the current incident,” Forystek noted. “A lot of these incidents tend to happen in the same areas, same neighborhood, and even the same house.”

Total Stations and Laser Scanners on the Scene

When working for the Flint PD, Forystek used a Sokkia SRX 5 robotic total station with Archer evidence collector and MapScenes EvR evidence software. He says the combination of speed and accuracy plus the amount of evidence he gathered made the total station a highly effective tool for his crime scenes.

“If you go into a nightclub with a 3,000- to 4,000-square-foot area using a tape measure, you’d have to walk around it numerous times and may even have to traverse around some evidence,” Forystek said. “Using a reflectorless total station for an inside scene like this, I can stand in one location and shoot just about everything I need.” Sometimes indoor shooting scenes can be too small for a total station to map. In this case, although rare, Forystek manually measures the scene and feeds the points into his MapScenes software to create a professional diagram.

Which tools to use for documenting these scenes is a personal choice depending on the investigator. It’s safe to say that the total station, while not the only tool chosen, is widely used. However, the laser scanner, a newer tool for scene documentation, also is being used where budgets will allow. A laser scanner, like Topcon’s GLS-1500, enables an investigator to scan a crime scene quickly, collecting upwards of 50,000 measurements per second.

A high-resolution digital camera is embedded within this scanner, providing the user with valuable photos of the scene over which scan data can be overlaid. Users find that they can virtually return to any crime scene captured with a laser scanner to make additional measurements or to verify what witnesses might have seen based on the scanned scene. The scanned data also can be converted to 3D exhibits and simulations to help jurors understand the layout of a crime scene.

An advantage of laser scanners is that the user does not need to focus on one measurement. The scanner will capture millions of data points as it scans the entire scene.  When documenting indoor shooting or crime scenes, line-of-sight issues are more complex with 3D mapping/scanning. Therefore, the number of scans needed to cover an overall area increases substantially. When using a laser scanner for indoor crime scenes, investigators may want to scan both before and after a body or any items such as chairs and tables are removed, or with doors both opened and closed. After all, the more-confined space of an indoor scene can allow for the disruption of physical evidence.

3D Priorities

Brad Joice, owner of Forensic Mapping Services, in Barrie, Ontario, Canada, specializes in mapping indoor shooting scenes. He notes that mapping a scene is one of the final steps in a shooting scene investigation process to avoid disturbing scene evidence. For a shooting scene, he divides it into mapping priorities.

The first priority area is that of the actual shooting or the area in which the physical evidence lies: blood, bullet holes, cartridge casings, weapons. “I measure this with a total station,” Joice said. “That way, I’m gathering all of my 3D measurements so I can create a 3D diagram for investigative use and/or for court presentation.” The second priority area is the rest of the building where the shooting scene happened, for which Joice uses a handheld laser distance-measuring device.
Once data points and distances are collected via the total station and laser distance device, Joice draws a 2D diagram. Once this is created, “I can take it one step further and create a 3D diagram of that room to assist with trajectory analysis or court presentation,” Joice said. “I can collect points and feed them into the MapScenes Evidence Recorder software, then switch back to the total station and take additional measurements, right within the software, without having to create separate jobs or diagrams.”

Joice uses a Sokkia 530R3 reflectorless total station that can also be used with a prism. “That’s critical for inside shooting scenes because a prism may be too big and bulky, and you can’t get into corners, plus it’s hard to shoot walls,” Joice explains. “You’re dealing with small, confined spaces that don’t make sense for a prism, so it’s not productive. The total station needs to be in prismless mode,” Joice said.

Another aspect Joice values with his selection of total station and evidence collection software is the seamless integration if offers. “It saves time in the long-run because the diagram is two-thirds complete just by virtue of downloading it to the drawing program,” Joice said. It’s being created and displayed to the user in real time on the evidence-collection software.

Regardless of the mapping technology tools used for indoor shooting scenes, whether they be total stations, laser scanners, or just a steel tape measure or measuring wheel, the investigator has only one chance for processing and documenting scene evidence. Therefore, the investigator’s skill in knowing what evidence to map and having the right tools to accomplish this are paramount. 


Equally important is the ability to produce a clear and detailed 2D or 3D diagram so that jurors can understand the likely events leading to the crime scene and the integrity of the data collected. For example, in the MapScenes Evidence Recorder software, once evidence points are collected, no one can go in and modify those points without the software logging all modifications. If changes to points are made, the user must then defend these changes in court.  Therefore, Joice says, “The most crucial part of measuring any of these shooting scenes is accuracy regardless of what tool or technology you’re using.” Furthermore, not every crime scene will be represented as a 3D diagram. “We often use 2D because prosecutors rely on photographs a lot,” Forystek said. “The 3D is good for showing bullet trajectories because the path of the trajectory shows all the measurable points. And it shows elevation, distance, and perspective,” he added. This is where the evidence collection software proves its mettle. Once the software collects and displays all of the evidence points on the data collector’s screen, the user can move a 3D drawing around the scene and create a perspective that shows the scene in its most compelling manner. 

Surveyors May Aid Defense 

How can surveyors interested in pursuing forensic work enter this fascinating field? Forystek suggests surveyors may be able to get legal defense casework. “For example, when using a total station to take your points, do it consistently,” Forystek said. “Then, as you go to court more often you will gain confidence with how you testify in court as to how you mapped the evidence.” 

Forystek thinks at some point defense attorneys will need to start finding experts in mapping crime scenes. “There will be a niche in there for surveyors who really understand the total station and the software and who will be able to come into court and work on the defense side and throw in some doubt as to how evidence may not have been collected properly,” Forystek said.

Joice has some additional advice for surveyors who might wish to parlay their surveying skills, especially with a total station, into the forensic arena. “The biggest caveat is take lots of measurements [in this field],” Joice said. “It takes a lot more measurements to create an accurate 3D diagram. You can’t take too many measurements.”

Above all, remember that from the start of any crime scene investigation, especially one involving an indoor shooting incident, you are documenting the scene for eventual litigation. “If there was not litigation,” Forystek offers, “we could just take some photos. But we have to be more precise [with shooting scenes] because there’s going to be criminal prosecution and some civil litigation involved.”

Robert Galvin writes about indoor and outdoor crime scene documentation and technology for surveying and law enforcement publications. Galvin resides in Oregon City, Oregon, and can be reached at


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