Prosecutors might seek a second opinion about the mental capabilities of a Lawrence man charged with murdering his elderly father by neglect.

Despite a defense attorney’s complaint that it should have happened weeks ago, a judge on Tuesday authorized Dist. Atty. Christine Kenney’s office to get its own expert evaluation of Timothy D. Harrell.

An expert hired by the defense has testified that Harrell, a 44-year-old window washer and maintenance worker, is mentally retarded and goes through life functioning at the level of a 3-year-old. He’s charged with second-degree murder in the November 2002 death of his 84-year-old father, Henry Ford Harrell.

Harrell’s defense attorneys gave notice in September that they planned to rely on lack of mental state as a defense at trial. That means the state has an opportunity to hire its own expert.

District Court Judge Michael Malone on Tuesday gave prosecutors until March 8 to conduct and submit theirs, despite defense attorney Alice White’s complaint that the state was dragging its heels.

“They were clearly on notice that we would be raising that at trial,” White said. “They’ve been aware of this for a long time.”

Whether the state actually hires an expert depends in part on who’s available, prosecutor Angela Wilson said.

Malone has yet to rule on a number of pre-trial motions filed by defense attorneys, including one that challenges whether Harrell’s statement to police was made voluntarily.

Harrell’s trial is scheduled to begin March 29.