Knott Laboratory provides forensic engineering and animation, Civil & Structural, and Fire & Explosion Investigation services to reconstruct accidents.

High Profile Case: Daniel Perry Murder Trial

 

The Background

In 2020, Garrett Foster was shot and killed during a Black Lives Matter demonstration in downtown Austin, Texas. Mr. Foster was a participant in the demonstration and openly carried an AK-47 rifle while walking through the crowd (which is legal under Texas law).

Daniel Perry, an on-duty Uber driver, had driven into the crowd. His statement was that he was following directions on his phone. He was also legally carrying a handgun in his vehicle. Mr. Foster approached Mr. Perry’s car holding the rifle at Mr. Perry who then fired at Mr. Foster, killing him. Mr. Perry fled the scene then called police and reported what happened, claiming he fired in self defense.

Knott Laboratory was hired by the defense attorneys to answer two important questions in the case:

  1. What was the speed of the vehicle and was it consistent with movements intending to run people over and cause harm (as was the claim of some witnesses for the prosecution)?
  2. Where was Mr. Foster positioned outside of Mr. Perry’s car and at what distance?

 

The Process

The role of forensic engineers is to conduct scientific analysis and provide conclusions strictly based on the science. Knott Laboratory’s Digital Media Forensics™ process uses cutting-edge technology to bring clarity from chaos in cases such as this.

First, using a 3D laser scanner (Leica RTC360), we conducted 23 laser scans of the area in downtown Austin where the incident occurred. This laser scanner captures up to two million points per second and HDR imagery, resulting in a point cloud, or digital twin, of the scene. This provides our forensic engineers with a scientifically accurate model from which measurements can be taken.

The point cloud in this case has over 561 million data points. The density of this point cloud provided the ability to take measurements within 6mm accuracy.

The next step was to reconstruct the scene as it was throughout the incident. To do so, our visualization experts used the multiple videos and images collected as evidence. They include:

  • Dash camera from a separate ride-share vehicle
  • Surveillance footage from a nearby bank
  • Multiple cell phone videos from bystanders
  • Images taken by a freelance photographer

Using processes called videogrammetry and camera matching, the visualization team placed these videos into the point cloud, syncing their exact locations within the scene.

We created a bi-ped model of Mr. Foster using footage of him near the vehicle. With measurements accurate to within 6mm, the model was able to accurately reflect Mr. Foster’s height and frame.

The same step followed to determine the position of Mr. Perry’s vehicle throughout the incident. Accurately scaled virtual models of the vehicle were placed into the scene, matching its orientation and position as shown in the video.

 

Findings

With the scene reconstructed, speed and distance analysis could now be conducted.

Question 1 – What was the speed of the vehicle and was it consistent with movements intending to run people over and cause harm?

By analyzing the position of Mr. Perry’s vehicle frame-by-frame, we were able to measure his speed as he turned a corner, entering the area in question, among the crowd of demonstrators.

Mr. Perry’s vehicle started to turn at 11.9 mph, quickly slowed to 10.7 mph, continued to slow to 7.3 mph, then braked to a stop.

Since Mr. Perry’s vehicle decelerated throughout the turn prior to stopping, it is not consistent with movements intending to use the vehicle to cause harm.

 

Question 2 – Where was Mr. Foster positioned outside of Mr. Perry’s car and at what distance?

Photogrammetry was performed specifically on one frame of a video at 1-2 tenths of a second before the first shot was fired. This frame showed Mr. Foster standing outside Mr. Perry’s vehicle, though with the image alone it’s impossible to determine the distance.

Based on our analysis, Mr. Foster was positioned 18 inches from Mr. Perry’s car. He had his right arm up, his left shoulder pointed to the vehicle, and body positioned in what’s called a “bladed stance.” This is a position where one foot is in front of the other and the body is at an angle, a typical stance for holding a rifle. Knott was unable, due to the limitation of video evidence, to identify the position of the rifle being held by Mr. Foster.

The Outcome

This was a highly contentious case. Based on other evidence presented at trial calling into question Perry’s intent, the jury convicted him of murder. He was sentenced to 25 years. However, Governor Greg Abbott pardoned Perry shortly after the Texas Board of Pardons and Paroles recommended a full pardon.

Knott Laboratory does not provide analysis or testimony on whether the use of lethal force was appropriate. The Digital Media Forensics™ process creates scientifically accurate scene reconstructions from which proper analysis can be conducted. The goal of our expertise is to bring clarity from chaos, providing a foundation from which juries, judges, and appropriate authorities may do their job.

KXAN News Austin coverage of our expert testimony