IBERVILLE PARISH - Opening statements began Tuesday in the trial of a former assistant principal, accused of murdering a woman who was said to be pregnant with his child back in 2016. 

A key witness is the victim's child, who took the stand today.

The trial of Robert Marks began with high emotion as his attorney accused detectives of not reviewing all the evidence against his client.

Marks is charged with fatally shooting Lintell Washington back in 2016, who was seven months pregnant at the time.

The accusation is he tried to cover up an affair he had with Lintell. The only witness to her killing: her then three-year-old daughter.

The evidence presented in court Monday was a video that showed the little girl being interviewed by a worker from the Children's Advocacy Center in Baton Rouge.

In the beginning of that video, you see the little girl who looks like she's coloring at the table and is being asked questions on what happened that day, June 9th, 2016. The interview asked her, "what happened that day?" 

The girl said she had just gotten out of the car and she was crying too much because there was blood in the car. The interviewer did ask her what happened to mommy? And the little girl said 'mommy's hurt, Mr. Robbie hurt her.' 

The question at hand is who killed Lintell,

Iberville Parish District Attorney Tony Clayton says he believes the evidence against Marks—including the taped interview with Lintell's daughter—is strong.

"I think it's all damming, we putting forth evidence that we believe that at the end of the day will convince the jury," Clayton said.

BRPD Detective Jonathan Medine recounted what happened that day.

Medine says he responded to a call of a child found wandering around in a parking lot. When he arrived on scene he saw the three-year-old with blood on her feet. She told Medine that her mom was hurt.

Later that night, he was asked to supervise a taped forensic interview of the little girl, the recording played in court.

The interviewer asked the child about a lake, and if her mom was in it.

Defense attorney Lon Burns argued that the video showed nothing more than leading questions since the girl never brought up anything about a lake on her own.

Lintell was later found dumped in a ditch in Iberville Parish. Her daughter took the stand Tuesday so that video could be shown.

"Our purpose of putting the child on the stand today was to one, show that the child was available, subject to cross-examination, and two, that that was the child that gave the statement when she was three years old. So, to have a nine-year-old child now testify about what happened at three years old is somewhat complicated. So, by calling the child up, I was able to get in the video that they took at the time of the murder," Clayton said.