AUSTIN (KXAN) — Testimony from a photogrammetry expert in the Daniel Perry murder trial disputed eyewitness accounts that Daniel Perry sped into a crowd of Black Lives Matter protesters before he shot and killed Garrett Foster in downtown Austin.

Perry is accused of murder and aggravated assault with a deadly weapon in the July 2020 death of Foster. Perry entered a not-guilty plea in court last week.

The expert, Jason Evans, who is an engineer, testified in court on Tuesday. Evans said they performed a laser scan of the scene on Congress Avenue to analyze a number of things, including the speed of Perry’s car. This was based on a dashcam video from an Uber driver who testified in the first week of the murder trial.

“We now have a 3D rendering of the move and the turn of Mr. Perry’s vehicle,” Evans said. “Mr. Perry starts out at 11.9 miles per hour, starts to deaccelerate, or slow down.”

Several witnesses, who were at the protest demonstration the night Foster died, were called to testify during the first week of the trial. They recalled seeing Perry’s car drive forward into a crowd of protesters. The protesters, which included Foster, became “incensed” at the presence of the vehicle, a witness said.

During her testimony last week, Foster’s fiancée, Whitney Mitchell, said the car sped toward them. She testified that’s when her fiancé’ jumped in front of her, as she was near the driver’s side of the vehicle.

Evans said laser scans — paired with video provided by witnesses — also helped him determine Foster was about 18 inches from Perry’s driver-side door with his rifle a tenth of a second before he was shot.

A 3D rendering from Jason Evans’ analysis, showing the distance Garrett Foster was from Daniel Perry’s car before he was shot and killed during a BLM protest. (KVUE Pool Camera Photographer photo).

Evans was asked by Perry’s defense why some videos that captured Perry turning into the crowd, may show his car going faster at the turn. Evans said it could depend on the angle the video was filmed.

Evans said, while no data collection is perfect and does have a margin of error, he’s “completely confident” in its accuracy, which he used for his analysis.

In the state’s line of questioning, attorneys questioned the effectiveness of the equipment used to gather data.

“Experts in field have stated that there are many factors factoring into how well the system works,” an attorney with the state said. “It’s about the operator.”

Evans didn’t collect the data himself. He said his colleague did that, then Evans analyzed it.

“We train users,” Evans said. “All engineers use laser scanner on a regular basis.”

Still, the state questioned whether the data used to reach the conclusion that Perry slowed down as he turned into the crowd, was gathered properly.

“It would be nice to know that the operator, knew what the hell they’re doing,” the state said.

There was some analysis of evidence Evans didn’t do, he admitted. Evans said they didn’t use any overhead footage from the Halo Camera downtown, to determine the speed Perry was driving before he made his turn into the crowd.

“The more data you have, the more accurate results you’d have to present before this jury,” the state asked Evans.

According to the state, Evans is a retired police officer. He worked in Colorado for seven years, he told the court. Through his firm he works for now, Evans said he has been asked to be a guest by what the state describes as ‘pro-police’ podcasts. During his time on these podcasts, he’s been asked questions about laser data and analysis like what he used in Perry’s case.

This story will be updated by reporter Jala Washington. Follow her on Twitter for her live updates from the courtroom.