A man charged with killing an off-duty city police officer this year is seeking to change his plea from "not guilty" to "not criminally responsible," court documents show.

With the request to change his plea comes a trial delay. Yesterday, the Baltimore Circuit Court trial for Brandon Grimes was postponed from Sept. 11 to Nov. 2.

Grimes is a 22-year-old with a long arrest record who is accused of fatally shooting Detective Troy Lamont Chesley Sr. in what might have been a robbery attempt. Grimes' attorneys say in court papers that he also has bipolar disorder and has exhibited "bizarre behavior" over the years.

According to a motion filed recently, Grimes received nine years of schooling, much of it as a special education student. At age 10, according to the motion, the Social Security Administration determined him to be disabled because of a serious learning disability.

Chesley, 34, was shot to death about 1:20 a.m. Jan. 9 as he fumbled for his keys on the front porch of a house in the 4500 block of Fairfax Road. He had just finished his midnight shift. He fired his service revolver before collapsing.

Grimes was treated that morning for a gunshot wound to his leg. He was quickly charged with Chesley's first-degree murder.

Grimes' attorneys filed two motions -- a notice of incompetency to stand trial and a plea of not criminally responsible at the time of the alleged offense. They are seeking court hearings on both matters.

julie.bykowicz@baltsun.com