A Las Vegas mother pleaded not guilty by reason of insanity Thursday to killing her 6-year-old daughter with scissors after thinking she heard the girl speak and laugh in what she later told police was an "evil voice."

Danielle Yvonne Slaughter spoke clearly while answering a judge's questions and entering her plea during a brief arraignment in Clark County District Court. Judge Melisa De La Garza scheduled Slaughter to appear at a May 16 before the trial judge.

Slaughter, 27, remained jailed without bail. She faces a murder charge that could put her in prison for the rest of her life.

Her lawyer, deputy Clark County Public Defender Andrea Luem, said she isn't contesting Slaughter's competency for trial. Instead, Slaughter is claiming temporary insanity.

Prosecutor Pam Weckerly declined to comment outside court.

Slaughter was found naked, barefoot and bloody March 11 near her home in northwest Las Vegas shortly before her live-in boyfriend summoned police. They found Slaughter's daughter, Kyla Franks, dead in a bedroom and a pair of scissors nearby.

A frenzied Slaughter told police who took her to a hospital that the blood on her hands was from the "lamb of God."

"Did I kill my daughter? Is she dead?" Slaughter later asked homicide detectives.

In a recorded interview, Slaughter told investigators she had been having trouble sleeping since she started taking a caffeinated, over-the-counter weight-loss product four days before the slaying. She said she slept just one hour the night before.

Luem said Thursday it was too early to tell if lack of sleep and taking the dietary supplement had any effect on the slaying.

Slaughter told police she kept her daughter home from daycare the day of the slaying because she felt an "evil presence" in the house.

She said the two were sitting on the bed when the girl spoke in "evil words," laughed "in an evil voice" and clawed and kicked at her, police said in an arrest report. Slaughter told police she picked up the scissors and struck the child several times.

"One of the first things that Danielle told the detectives was that she could not believe she had killed her daughter," the police report said.