ROCHESTER, N.Y. – Testimony began Tuesday in the Charlie Tan murder trial. The Pittsford teen is accused of killing his father in February, but the polarizing part of this case is the alleged abuse that Tan and his family were subjected to leading up to the shooting.

Prosecutor Bill Gargan said this case is about Charlie’s deliberate decision to kill his father Jim, but the defense argues that this case is anything but simple.

Testimony began Tuesday with 911 operator Danielle Waters testifying that she took a call from Jean Tan, Charlie’s mother. On the Feb. 9 call Jean is distraught, crying and dispatchers have a hard time understanding her.

Jean tells 911 her husband’s dead and that her son shot him because, quote, “he was trying to protect me.”

The first Monroe County Sheriff’s deputies who arrived on scene that day took the stand next. Deputy Christopher Cooper told the court that as he was taking Charlie into custody, Charlie told him his father was dead and that he had to do it because he was going to kill his mother. Another deputy testifies he overheard Jean telling EMS workers that her husband beat her.

Thus is the crux of the defense’s case, the alleged abuse that existed in the Tan home long before Jim was killed. In openings, defense attorney Brian DeCarolis asked jurors to think about what would force this former class president, sophomore at Cornell and “great kid” to come home and kill his father.

“Domestic violence was a big part of the jury selection. It’s an important piece of this case,” DeCarolis said. “What happened, whenever it happened, because of that domestic violence piece. It’s the why behind what happened.”

Prosecutor Gargan argued that Charlie made very deliberate decisions the day he shot his father, to come back home to Pittsford, to point the shotgun at this father and to shoot him to death. Gargan says Charlie shot Jim three times while he was sitting at his desk. A desk that Gargan says was undisturbed.

Gargan argues the act was done out of hatred for his father and that there was no immediate threat or danger in the moment Jim was shot.

“The context of many justified homicide cases involves a horrific unfolding event in which someone has no choice,” Gargan said. “I used the phrase choice and freedom in my opening to show that each step that was taken was a step that did not have to be taken."

Jurors in the afternoon were shown some very graphic photos of the Tan home after the murder and of Jim Tan’s body. It was a difficult moment for those in the courtroom and there were many supporters there for Charlie who have been by his side since this happened.

The jury, made up of mostly women, is expected to hear dozens of witnesses as the trial continues.