BRENTWOOD — A judge allowed a former Plaistow state representative indicted for sexual assaults he allegedly committed in the 1970s a delay in determining if he is competent to stand trial.

Prosecutors and defense lawyers appeared before Judge Marguerite Wageling on Monday to request that a competency hearing for Robert Vlack, 85, be postponed for two months.

Vlack has already undergone two competency evaluations after his defense lawyer raised concerns about whether his client was aware of the court proceedings under way against him.

Assistant County Attorney Brad Bolton told Wageling on Monday that evidence showing Vlack may have exhibited signs of “malingering” warranted a further evaluation.

Defense lawyer Gerald LaFlamme said he had no objection to Bolton’s request.

Lawyers and medical experts have been wrestling with the question of Vlack’s competency for more than a year.

He was indicted on 11 counts of aggravated felonious sexual assault by a grand jury in February 2010.

Prosecutors say Vlack began assaulting the girl in January 1975 when she was 15 years old. The alleged assaults were ongoing until about June 1976, according to indictments.

LaFlamme had argued at the outset that prosecutors should not have pursued the case because the statute of limitations ran out years ago. The defense argued that Vlack was an active resident of New Hampshire between 1981 and 1982, and was part of a committee that oversaw construction of the Seabrook Power Plant.

Prosecutors countered that Vlack left New Hampshire in 1981 to live in Connecticut, which froze any expiration on the deadline to seek criminal charges.

Investigators researched real estate holdings, divorce proceedings and other records to verify when Vlack left the state, prosecutors said.

A month after Vlack’s indictment, he was diagnosed with memory loss by the Veteran’s Administration Hospital, according to court records.

LaFlamme said in a court filing that Vlack had been diagnosed by a psychologist with dementia.

It’s unclear how the latest evaluation may affect the pending criminal charges. But if lawyers move ahead with the competency hearing this fall, it will be left up to Wageling whether Vlack is competent to stand trial.

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James A. Kimble may be reached at JKimble@newstote.com.