Seddique Mateen, the father of the Pulse nightclub shooter, was an F.B.I. informer for over a decade before facing an investigation into financial transfers abroad, a lawyer for the shooter’s widow said in a weekend court filing.

The lawyer, Fritz Scheller, said in a Sunday motion that the case against the wife, Noor Salman, 31, should be dismissed because prosecutors waited until Saturday, after they had rested their case, to reveal to him the relationship that Mr. Mateen had with the authorities.

“It is apparent from the government’s belated disclosure that Ms. Salman has been defending a case without a complete set of facts and evidence that the government was required to disclose,” Mr. Scheller wrote in the motion.

Ms. Salman faces charges of aiding and abetting her husband, Omar Mateen, in the shooting in Orlando, Fla., in which he killed 49 people and wounded 53 others. Her trial began this month. If convicted, she faces life in prison.