3D Laser Scanning and the Trayvon Martin Case

by Tate Jones

about 2 years and 7 months ago

Tagscrime scene, forensic investigation, laser scanning

We have all heard and seen the news reports of the terrible tragedy that occurred in the altercation and subsequent killing of Trayvon Martin by George Zimmerman.

The case will be prosecuted on the basis of whether Zimmerman was acting in self-defense or whether he was stalking Martin and therefore the aggressor, and his fate will likely be decided by a jury. 

Watching the extensive coverage of this case, I noticed a laser scanner on the scene in some of the many news reports. I don’t know how the data collected will be used in the case, if it will be used at all, but I do know many ways that it could be used.

Until recently, the best way to thoroughly document a crime scene was to take a series of photographs and record lots of notes and measurements as a way to document what happened.  But as soon as a scene is released, it is contaminated, making it unlikely that more usable evidence will be found. 3D laser scanning has changed all of that.

First used on crime scenes by the FBI, Secret Service and Scotland Yard, laser scanning is now becoming a “best practice” for the documentation of a homicide. Police departments all across the U.S. are purchasing high definition laser scanners to use in their crime scene investigations. There are many reasons for this trend, but here are just a few:

  • The 3D element: Scanning a scene in 3D enables all of the evidence in the scene—from the buildings and sidewalks to parked cars and surrounding areas—to be preserved in three dimensions. This means you can look at the scene from every possible view, not just the angle of the photographer and camera.
     
  • Data capture: As cases progress, evidence might emerge later that was not spotted originally. If you have done a thorough job of scanning, objects like drink cups, candy wrappers or even potential weapons that were unknown at the time can be seen in the scan. This has proven to be an excellent tool for the prosecution in criminal trials. Many cases have been helped by data captured in a scan that was totally unknown at the time of the initial investigation.

So how could this technology be used in the Trayvon Martin/George Zimmerman case?

The killing occurred on a sidewalk between two adjacent apartment buildings. Many witnesses have testified that they heard and saw all or part of the incident from inside their apartment. 

A thorough laser scan could easily capture the view from each window in the adjoining apartment building. Armed with this data, if Witness A later says he saw the incident from his window and Witness B says she saw something from her window, investigators could easily use the 3D point cloud (dense scan data) to go behind the windows referenced by the witnesses and check the exact line of site.

This view would essentially allow investigators to stand in individual apartments and view the crime scene in 3D, enabling them to confirm or refute the testimony of the witnesses as to what they said they saw.

This extremely detailed data would also enable them to determine if something like a lamp or curtains was inside the apartment and obstructing the witness’ view.

This type of scan actually exonerated an accused person in a California case, in which a man was accused of shooting his wife from his house, across the road from a hill where she was walking. 

Several witnesses reported seeing him shoot her. As it turns out, the police scans showed that the line of sight from the man’s window to the path the victim was walking on was blocked by low trees and high bushes. No one inside the house could have seen the victim from this viewpoint.

This knowledge ultimately led police to continue their investigation and eventually catch the guilty party.

High definition scanning can also be used to compute the exact location of a shooter. If a bullet enters a house from the outside and goes into the wall across the room—and that room is then scanned—the exact path of the bullet can be shown with a great degree of accuracy. 

If multiple shots penetrate the house, the evidence is even more compelling. Because of the multiple trajectory lines that are formed by multiple bullets, the area of shots will be very precise. This data can help determine if the shots came from a house across the street or from a car parked in front of the house, for example.

The tunnel that Princess Diana’s car crashed in is still probably the most thoroughly scanned crime scene in the world. The scan data, combined with the physical data, was able to help determine the precise path of the car.

Similarly, there have been several scans conducted of the grassy knoll where a second shooter of President Kennedy was allegedly positioned. In this case, however, there was no conclusive evidence.

I don’t know how the Trayvon Martin-Zimmerman case will ultimately be resolved. I’m not even sure if the authorities with the data completely understand how it can be used. But I do know that courts across America have allowed laser scan data to be introduced as evidence in all types of trials, both criminal and civil.

What used to be viewed as an unproven technology has now become much more common and mainstream. 

Tate Jones

Tate Jones is president of 3D Laser Surveys, a Division of LandAir Surveying. He has more than 40 years of experience in land and aerial surveying and is a nationally recognized expert in the field of 3D data capture.


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