SALT LAKE CITY (AP) – A Utah teenager accused in the strangling death of a 12-year-old neighbor girl has also been charged with sexually assaulting her, a judge said during a Thursday court hearing.

Prosecutors say the 15-year-old boy lured victim Kailey Vijil from her West Valley City home by knocking on her door and asking for help looking for a lost cat. Police say the defendant also tried to lure at least one other neighborhood girl from her home earlier that night.

Kailey’s naked body was found a few hours later in an overgrown horse pasture near their neighborhood in a Salt Lake City suburb. A shirt was wrapped around her neck, police said.

Judge James Michie informed the boy about the child rape charge as he explained why he had ordered him handcuffed for the hearing.

RELATED: Utah Teen Accused Of Luring Girl, 12, With Lost Pet Ruse, Strangling Her In A Field

The new count made public Thursday was filed about a month after the girl’s July 17 death, after DNA tests matched evidence found on her body to the teenager, according to charging documents.

The Associated Press is not naming the defendant because he is a juvenile. He appeared in court wearing a green jumpsuit, and nodded in response to the judge’s slow, careful explanation of the court process.

His lawyers are investigating whether the teen is mentally competent to stand trial in the case, said attorney Michael Sikora. He said the boy’s records indicated he’s been treated for attention deficit hyperactivity disorder, or ADHD, but his condition may be more complicated than that.

“We have to get as much information as we can,” he said. Sikora declined additional comment following the hearing.

The teen is also facing an aggravated murder charge. Prosecutors want him tried as an adult on both counts due to the seriousness of the allegations. Though that charge would normally carry the possibility of the death penalty, the boy won’t face it because he’s a juvenile.

He is due back in court on Oct. 15. Prosecutor Patricia Cassell agreed to defense attorneys’ request for extra time to prepare in the case.

“We want to make sure all of this is done right,” she said.