A state judge has delayed a January trial in the killing of an eastern Montana teacher after state health officials requested more time to conduct a competency evaluation on the defendant.

District Judge Richard Simonton did not set a new trial date in his Wednesday order.

Defendant Michael Keith Spell of Parachute, Colo., could face the death sentence if convicted in the January 2012 murder of Sidney High School teacher Sherry Arnold.

Spell's attorneys say he is not fit for trial because of mental disabilities. He was admitted to Montana State Hospital in Warm Springs last month.

Simonton's order extends Spell's stay at the institution until mid-January.

Co-defendant Lester Van Waters, Jr., pleaded guilty under a deal with prosecutors. He has not yet been sentenced.