SPOKANE, Wash. -

Avondre Graham, the Spokane teenager suspected of stabbing a woman while she was walking her dog last year, will undergo a mental evaluation to determine if he's fit to stand trial.

Graham's attorney has asked that her client receive a sanity evaluation before he's prosecuted for the murder of Sharlotte McGill. Police say Graham admitted to killing McGill last May and attacking two other women jogging along the Spokane River.

The public defender representing Graham claims the 18-year-old may be too mentally disabled to assist with his defense and is laying the groundwork for Graham to plead not guilty by reason of insanity.

Graham's trial was supposed to get underway next month but now his case has been delayed while doctors at Eastern State Hospital test his mental abilities.