A convicted murderer testified in graphic detail Tuesday that her then-boyfriend, Dominique Dantoni Smith, slit the throats of his former girlfriend — after first knocking her to the ground with a baseball bat — and two of her young children at a BREC park near Zachary in 2008.

Trendall Lashel Matthews told an East Baton Rouge Parish jury that she held Jessica Johnson Palmer down while Smith cut her, and also held on to 3-year-old Juan Palmer Jr. while Smith cut him.

Jessica Johnson Palmer, 23, of Baker, and her son, Juan Palmer Jr., died in the May 4, 2008, attack at Doyle’s Bayou Park on Pride-Port Hudson Road.

“I’ve asked God to forgive me,” Matthews said. “I can’t take that (the tragic events) back.”

Palmer’s daughters — Paige Johnson and Robbyn Palmer, who were 4 years old and 6 months old, respectively, at the time — were left overnight in the park for dead but survived. Paige’s throat also was cut.

Smith, 31, of Wilson, is Paige Johnson’s father. He is standing trial on two counts each of first-degree murder and attempted first-degree murder. The trial will resume Wednesday. State District Judge Tony Marabella is presiding.

Smith faces a mandatory sentence of life in prison if convicted of first-degree murder because East Baton Rouge Parish prosecutors earlier this month withdrew a notice of intent to seek the death penalty after concerns were raised about the welfare of Paige Johnson, who is expected to testify at the trial. The girl is now 9 years old.

The only witness to testify Tuesday was Matthews, who is serving two life sentences at the Louisiana Correctional Institute for Women in St. Gabriel after pleading guilty in the case in 2011 to two counts each of first-degree murder and attempted first-degree murder. She avoided a possible death sentence by doing so.

Matthews, 25, of Jackson, testified she and Smith had driven to the park that Sunday afternoon when Palmer showed up with her three children. Matthews said Smith, Palmer and the children went walking into the park, and after a while, she heard load yelling and screaming.

Matthews, who testified while wearing LCIW prison clothes, said she then walked to where Smith, Palmer and the children were, and Palmer was not happy to see her. Palmer and Matthews are cousins. Matthews said an angry Palmer began to walk away when Smith hit her between the shoulder blade and back of the head with a bat that Smith and Matthews had just bought from a nearby store. Smith hit Palmer once more with the bat in the head, Matthews said.

“Dominique grabs her by the back of the head and makes a cut,” she said, demonstrating for the jury how Smith cut the neck of Palmer, who was lying face down.

A sheriff’s deputy had to unshackle Matthews’ hands so she could perform the demonstration.

Palmer was “wheezing and gasping” when Smith turned her over, Matthews said.

“He continues to cut her. Blood is going everywhere,” she said.

Matthews said she grabbed Palmer by the feet and dragged her a short distance to hide her body.

Matthews said the next thing she saw was Juan Palmer Jr. starting to walk away from Smith.

“He (Smith) grabs him by the back of the shirt and makes the first incision,” she testified.

Matthews said she put the boy in a ditch, but he tried to climb out.

“I pushed him back down,” she said.

Smith then turned his attention to Paige Johnson, Matthews said.

“After he walks up on Paige and makes the first incision, he stops,” she said.

Matthews said she could not recall where Robbyn Palmer was during the ordeal.

She also said she could not recall if Jessica Palmer, Juan Palmer Jr. or Paige Johnson said anything during the attacks.

“I’m not focused on noises,” she said.

Matthews said she and Smith drove off and burned their bloody clothes. She also said Smith threw an item from the car. She said she could not identify the item because it was wrapped up.

After Matthews and Smith were arrested and jailed, Matthews said Smith wrote her numerous letters. In one letter that Matthews read for the jury, Smith stated, “The only way I go home is if you do. If you want to send me home ... it’s up to you.”

Matthews also said she wrote many letters to Smith. She signed some of them, “the real Mrs. Smith.”

Matthews denied signing affidavits that said she committed the crimes in the park and Smith was completely innocent.

Smith’s attorneys will cross-examine Matthews on Wednesday.

Sheriff’s detectives have testified previously at pretrial hearings that Smith implicated himself and Matthews in the attacks. Smith said he and Palmer went for a walk, during which he grabbed her hands while Matthews attacked her, according to an arrest affidavit.

Smith was the target of a paternity and child-support petition involving Paige Johnson, according to West Feliciana Parish court records. Palmer filed the petition against Smith in November 2006.