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Much of crime scene work is identifying, documenting and collecting evidence. Evidence is not always a physical object or property that may be documented and collected. The absence of something can be powerful evidence. When documenting evidence (or the lack thereof), the investigator should ensure the process is thorough and complete. Photography is standard practice and an indispensable aspect of an investigation. 

In the past, when an investigation also required a diagram, field sketches were often scribbled in one’s subjective notes. Sometimes, long after a scene is released, new information is learned which would have changed the way an investigator initially documented the scene.

Now, investigators can collect accurate data faster and more efficiently. 3D laser scanners are becoming more and more prevalent in the quest to document and preserve forensic evidence. Speed, accuracy and visualization are the name of the game. 

3D laser scanning is the process of capturing millions of data points of a real-world environment (a 3D point cloud), allowing you to view that environment virtually. These point clouds can be used to produce accurate, realistic, 3D computer graphical models for use in a variety of applications including investigations of crime, accident and fire scenes.

Such systems include specialized camera systems, ground and aerial-based cameras, and software that converts photographs into 3D views.

How does 3D scanning help the investigator document evidence, interpret fact and discover truth? As an objective collector of data, a 3D scanner makes no decisions as to what should be collected or disregarded. On normal, full-capture settings, a scanner will collect all data within its field-of-view, density and distance parameters. Though the operator may elect to limit some aspects of data capture, the documentation process is much more objective than manual measurements. It is not uncommon for 3D scanners to collect data on scene which proves useful at a later date, according to officer.com.

3D laser scanners are accurate to millimeters. These highly accurate scans can take less than two minutes to capture. The ability, in some cases, to collect over one million points per second answers the need for volume. Scans and high-quality images are captured in a fraction of the time it used to take with the scanners of yesterday. 

These systems are also becoming ever more portable. Laser scanners, once essentially restricted to cumbersome elements attached to large tripods, are becoming smaller and faster. Investigators can opt to use the more robust scanners; smaller, more portable scanners or even handheld, mobile units.

Only something observed and interpreted in its context is of use to the investigator. Considerations for the interpretation of evidence may include the location and identification of probative evidence; interrelationships between items of evidence; positions and orientation of evidence; and providing macro and micro views of the scene and its parts. 

3D data facilitates high accuracy and details in a series of scene diagrams. Within a good diagram, spatial relationships and evidence location and identification may be addressed. Trustworthy 3D data allows the investigator to view the scene from multiple viewpoints and analyze potential interrelationships between evidence on scene. Various measurements can be taken to quantify these relationships, thanks to the 3D technology.