The trial started Tuesday for a Fort Worth officer accused of aggressively taking down a 20-year-old man at Texas Health Harris Methodist Hospital in 2016 and lying to both police and a grand jury.
Jon Romer faces official oppression charges; this criminal trial is to determine whether he's guilty of perjury.
An indictment claims Romer knowingly lied to a grand jury after that incident, saying under oath that he'd told Henry Newson that he was under arrest before he hit him.
"This is a case about deceit, dishonesty and deception," prosecutor Russell Wilson said.
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Wilson told the jury he intended to prove through both security and body camera footage that the use of force came long before Newson was told he was under arrest.
At the time of the incident, Newson said he was waiting in the hospital lobby for a ride from his mom after he was released from a two-day stay.
Video shows he was first approached by a security officer before the conversation escalated.
Romer, who was working private security for the hospital at the time, approached moments later and confronted Newson.
"Hey get off the phone. Shut up. Get off the phone. Let's go," Romer is heard saying in the video.
The officer then places his hand on Newson's chest and pushes him backward, and seemed to take offense when Newson called him "bro."
"Bro?" Romer asks before he punches Newson in the face, grabs him around the neck and forces him to the ground.
Hospital security officers can then be seen piling on, surveillance video shows.
The prosecution claims Newson wasn't told he was under arrest until he was already on the ground.
"We had it forensically search to find out if that statement had ever been made prior to striking him, and it wasn't. It wasn't," Wilson said.
Though Newson spent two days in jail for trespassing and resisting arrest, the charges were later dropped.
Romer's defense did not make an opening statement Tuesday.
The first day in court wrapped up after only one witness took to the stand, Texas Health employee Reginald Jackson, who provided the video to attorneys.
The trial resumes at 9 a.m. Wednesday.
An earlier version of this story incorrectly reported Romer was a "former" officer. He has been placed on restricted duty and stripped of his gun and badge but is still an officer pending the outcome of the trial.