(DALLAS) — Witness testimony continued Tuesday in the trial of now-former police officer Aaron Dean in the 2019 fatal shooting of Atatiana Jefferson.

Dean is charged with murder in the death of Jefferson, a Black woman who was allegedly fatally shot by Dean inside her Fort Worth, Texas, home on Oct. 12, 2019.

Prosecutors began their opening statements by telling jurors about who Jefferson was. She was a 28-year-old woman who was living with her mother to take care of her, as well as address her own “severe health issues with her heart,” according to prosecutors. In that house, she helped raise Zion Carr, her then-8-year-old nephew who was present when she was fatally shot by police. She was “helping raise Zion, teaching him the responsibilities, day-to-day chores,” prosecutors said.

On that night, “[Zion] sees his aunt Tay — which is what he calls her — still playing video games and she’s up so, 8-year-old says ‘I want to play too.’ So, he gets up and he starts playing video games with her so they’re laughing, having a good time. Tatianna and Zion had no idea what was coming,” prosecutor Ashlea Deener said.

The defense began Monday’s hearing arguing for a motion to change the venue in which the trial is held because almost all of the potential jurors during jury selection had heard of the case. Judge George Gallagher denied the motion.

During opening statements, the defense focused on the gun in Jefferson’s hand in the moments before she was shot. The prosecution argued that Dean shot Jefferson before Dean could see a gun and before Jefferson could follow his commands.

“As soon as Aaron enters into the backyard, he sees a silhouette at the window,” Dean’s defense attorney Miles Brissette said. “Aaron sees that silhouette in the window and that silhouette has a firearm. That silhouette has a firearm with a green laser mounted on the front rail of that firearm pointed directly at Aaron, closer than me to you to the window.”

“The evidence will support he did not see the gun in her hand,” Deener said. “This is not a justification. This is not a self-defense case. This is murder.”

On the stand, now-11-year-old Zion told the court that he and Jefferson burned the hamburgers they were making, which is why they opened the door. They left the screen door open to let the smoke out, according to Zion and prosecutors.

He was the first and only witness to take the stand on the first day of the trial.

Police said they received a call just before 2:30 a.m. to respond to Jefferson’s home on East Allen Avenue after a neighbor called to say the front door was open.

Two officers arrived at the house shortly after and parked near Jefferson’s home, but not in front of the residence, according to officials.

The front door appears open in the body-camera footage, but a screen door looks to be closed in front of it. The officer doesn’t appear to knock.

Officials said the officers walked around the back of the house and that one of the officers observed a person through the rear window of the home and opened fire.

Zion said his aunt heard a noise, asked him about it and went to get a handgun from her purse. She walked toward the window, and then he said he saw her fall to the ground.

“She started crying and then two police officers came and got me,” Zion said.

Zion said his aunt did not raise her gun when she approached the window, however the defense attorney kept asking Zion questions about his recollection of an interview he did the night after his aunt was shot.

Zion had allegedly said during that interview that Jefferson had at one point raised the gun from her side, but Zion said he didn’t remember the details of what he did/said during the interview in response to the questions, visibly frustrated on the stand.

Fort Worth Police Lt. Brandon O’Neil said the officer who opened fire on Jefferson never identified himself as a police officer.

Officer Carol Darch, Dean’s former partner in the Fort Worth Police Department, took the stand Tuesday for cross-examination.

In her testimony, Darch said messiness inside the home made it look like there had been a home invasion of some sort, “like someone had methodically gone through that house looking for something.”

She said she and Dean didn’t announce themselves because of their own safety, as well as based on “open structure” procedure that trains officers to reduce the possibility that they might give an intruder into the home a chance to escape by alerting them of their presence.

Darch described the call as an “open structure” call, which refers to a call about a structure with an open door or window.

She later was asked to describe the “pyramid” style “Use-of-Force Continuum,” which calls for deadly force to be the last resort in addressing a threat. However, training does not require officers to take all steps before using deadly force if met with a deadly force.

“Deadly force is always met with deadly force,” Darch said. “We’re trained to stop the threat.”

Abriel Talbert, the call center employee who took the 911 call from Jefferson’s neighbor, told the jury that she included details about the house for police answering the call.

In her description to police, she included information that the caller shared that “both neighbors’ vehicles are in the driveway … and neighbors are usually home but never have a door open.”

She included those details “so the officer knows what’s supposed to be at the address, nothing out of the ordinary, other than the open door.”

Darch told the jury that she never saw Jefferson’s gun on the scene and never heard Dean announce that he saw a gun on Jefferson himself.

“I heard him give commands, I started turning. I was halfway through my turn and I heard the shot,” Darch said.

She later added, “The only thing I could see [through the window] was eyes, really. I couldn’t make out if it was a male or a female. I just saw someone in the window and I saw their eyes — as big as saucers.”

Darch got emotional on the stand when Zion came up in questioning. She said she was concerned about his well-being, as she said she tended to Zion’s care following the shooting.

Body camera footage released by the department shows the officer approaching a rear window of the home with his gun drawn. The officer sees the woman through the window and shouts, “Put your hands up, show me your hands,” and fires one shot.

The video seems to confirm the officer never identified himself as police before he opened fire.

Police officials said Jefferson was within her rights to protect herself and her nephew when she heard noises in her backyard and went to the window to investigate.

Court will resume on Wednesday.

There were concerns the trial would be delayed after Dean’s lead attorney, Jim Lane, died on Nov. 27, according to Dallas ABC affiliate WFAA, just one day before the jury selection in the case began. Lane had been ill and two other lawyers took over as lead attorneys in May, according to WFAA.

Monday’s court proceedings will only last half a day because of Lane’s funeral.

ABC News’ Amanda Su contributed to this report.

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