Jurors heard opening statements in the Edward Covington murder trial on Wednesday.

Covington is charged with killing his girlfriend, Lisa Frieberg, and her two children, Zachary, 7, and Heather Savannah, 2, in May 2008.

"Lisa's mistake proved to be fatal in allowing the defendant to move into her home," said prosecutor Sheri Maxim.

Detectives said the victims had been stabbed, mutilated and dismembered.

They said the family's dog was also beaten to death.

At the time, investigators said it was one of the worst crime scenes they'd ever seen.

Covington was found in a closet inside the mobile home. He was wearing only his underwear and was covered in toys and clothes. Investigators said he had blood on his palms and feet.

His attorney, Michael Peacock, said it's not a "Who-dun-it." He admitted in court that Covington committed the murders.

"The victims of these crimes were killed in a horrific manner. It's difficult to imagine a more overwhelming crime scene," said Peacock.

But Peacock said the gruesome details are actually evidence that Covington was insane at the time.

"His insanity will be shown in the appearance of the crime scene, what it looked like. It will be shown in the manner of death. Insanity will be shown in what was done to the bodies after death."

In his confession afterward, prosecutors said Covington told detectives Freiberg begged for her life while he demanded her bank card and car keys.

They didn't mention a specific motive but said Covington told authorities Freiberg loved him.   

In the middle of giving all these gruesome details surrounding the murders, Maxim said the defendant told the detectives, "She did nothing but love me and the kids loved me. She did nothing but love me."

If Covington is convicted of first-degree murder, prosecutors plan to seek the death penalty.