Updated

A once high-profile federal prosecution of an elderly Muslim cleric and one of his sons on terrorism finance charges has become bogged down in questions over the imam's mental stability and a legal fight over defense testimony.

A federal judge recently cast doubt about 77-year-old Hafiz Khan's mental fitness to stand trial. Prosecutors say Khan was the ringleader of a group that funneled tens of thousands of dollars to the Pakistani Taliban terror group.

If Khan is ruled incompetent, trial would be delayed for months or longer.

Prosecutors also oppose a defense request to allow three others indicted in the case and a fourth man to testify from Pakistan. Further delays are likely if the testimony is allowed.

Charges were dropped last month another of Khan's sons.