Trying to determine what actually happened at the scene of a crime and gathering evidence that is ultimately admitted and presented in court are major challenges for police departments and investigators.

The traditional method of crime scene reconstruction and evidence gathering involves an initial walkthrough and photo documentation. In the course of this investigation, it is critical not to remove or move items at the scene, because any disturbance can call the evidence’s validity into question; the evidence must be accepted as tamper proof in order to be authenticated and admitted in court.

It’s not easy to do. Investigators and forensics experts use total stations, which are portable crime scene mapping units that combine software, hardware, and data collecting sensors into an integrated mapper that records and maps evidence data points. 3D laser scanning technology is providing crime scene investigators with new analytics capabilities.

3D laser scanning tech

With 3D, not only can investigators record crime scenes and vital evidence data points, but they can take the 3D scans and review them at the office from multiple points of view, whether it be from the alleged victim, the perpetrator, or an observer.

The ability to model crime scenes without losing the integrity of recorded evidence and data provide greater insights into crimes and motives. The objective of this forensic mapping process is to better understand what happened at the crime scene, and to be able to convincingly convey this understanding in a way that the evidence stands up in a court of law.

There are two types of 3D laser scanners used in crime scene investigations: time-of-flight and phase shift.

Time-of-flight 3D laser scanners emit a single pulse of laser light that bounces off an object and measures the time for the reflected light to return to the distance sensor, and that can capture data points at speeds of up to 50,000 points per second.

Phase shift 3D laser scanners are more expensive than time-of-flight scanners and use infrared laser technology that can capture data points at up to 976,000 points per second.

“Once we leave the scene, we can revisit the scene again,” said John Lanneau, lead crime scene investigator for the Warner Robins, Georgia police, in an interview with WMAZ. Lanneau said that the scans can be viewed on computers or iPads, enabling police to look back for missed evidence, or to review and recheck crash measurements or the distance between objects, such as weapons. “All you have to do is click and drag,” he said.

3D modeling and predictive analytics

Just as important to present day investigations of crimes is the predictive value that analytics from crime scene evaluations can provide. Police responders and crime scene investigators already know that when it comes to investigating a crime scene and collecting evidence, the floor of the scene is the most likely place that the evidence will be found.

3D modeling of crime scenes can depict evidence data gathering in simulated scenarios for police and investigators for training purposes. These predictive analytics can pinpoint the key locations for evidence gathering at crime scenes so investigators and others are careful not to alter those locations; otherwise, the evidence’s validity might be questioned.

“By providing a working 3D model of the scene as first-responding investigators found it, law enforcement agencies are able to scrutinize and analyze the details long after the scene has been released,” wrote Jacob Dabrowski, in a 2010 Forensic Magazine article. “If necessary, this information can be presented to a jury — our engineers can practically turn a courtroom into the time and place in question — affording everyone present a view of the crucial details of a case, which had been deliberated blindly until HDLS (High Definition Laser Scanning) arrived on the scene.”

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