Was the father of one of the worst domestic lone-wolf terrorists in US history an FBI informant? Omar Mateen slaughtered 49 people in an Orlando nightclub in June 2016, declaring his loyalty to ISIS as he shot his victims. Now the prosecution of his wife Noor Salman may get derailed after court documents show that Seddique Mateen, the terrorist’s father, worked as a source for the FBI — and may be under criminal investigation himself:

Attorneys for Noor Salman are calling for a mistrial after they say new details from prosecutors reveal that Pulse gunman Omar Mateen’s father was an FBI source and is currently under a criminal investigation.

According to a motion filed by the defense, prosecutors sent an email on Saturday that stated Seddique Mateen was a confidential FBI source from 2005 through June 2016.

The email also stated that Seddique Mateen is being investigated for money transfers to Turkey and Pakistan after documents were found in his home on the day of the Pulse attack.

Salman’s attorneys claim the late disclosure of the information prevented them from exploring whether or not Seddique Mateen knew of his son’s plans to attack the nightclub on June 12, 2016.

By the time the prosecutors got around to notifying the defense of Mateen’s status, the trial had been underway for a week. The prosecution had already rested its case; the defense was expected to begin its case this week. That little tidbit of information could have been material not just to their presentation of the defense, but also during cross-examination of the prosecution’s witnesses.

How much of a game changer might this be? In their motion for dismissal or mistrial, Salman’s attorneys say this information would have opened up two other potential theories of the crime for them to investigate, with “strong support,” they argue:

“1) Omar Mateen and his father, rather than Ms. Salman, conspired to support ISIS; or 2) the FBI’s focus on Ms. Salman was based on its own motive to avoid responsibility for its failures with its own informant, Seddique Mateen, as well as his son,” Salman’s attorneys write.

Seddique Mateen was on the prosecution’s witness list, but was not called to testify in the trial.

That in itself is curious. While rules on discovery change a bit from venue to venue and get quite complicated, in general prosecutors are required to disclose any relationships between their witnesses and law enforcement, especially when it may be material to the case. Seddique Mateen certainly would have been someone with specific insight into the relationship between his son and daughter-in-law, which is no doubt why prosecutors had him on the witness list. So … why didn’t they call him to testify during their case? Did they not call him because they knew of his relationship with the FBI? If so, then the judge could reasonably conclude that they deliberately hid the information from the defense, and a mistrial would likely be the result.

Just on that basis, this trial seems on thin ice. Besides that, the defense raises an interesting question: what if it was the elder Mateen that helped his son cover up his intended terrorist attack, or what if it was both Mateen and Salman, working together or separately? The money transfers by Seddique discovered during the post-Pulse shooting investigation certainly should raise some eyebrows. Just where was that money going in Turkey and Pakistan? Let’s not forget Seddique’s own past, which was noted at the time, as a quasi-pro-Taliban online agitator:

Seddique Mateen hosts a program on a California-based satellite Afghan TV station, aimed at the Afghan diaspora in the in the U.S., called the “Durand Jirga Show.”

A senior Afghan intelligence source tells CBS News correspondent Lara Logan that the show is watched by some in people in Afghanistan but the primary audience is ethnic Pashtun Afghans living in the U.S. and Europe.

The Taliban Islamic extremist movement is comprised almost entirely of Pashtuns, and Mateen’s show takes a decidedly Pashtun nationalistic, pro-Taliban slant; full of anti-U.S. rhetoric and inflammatory language aimed at non-Pashtuns and at Pakistan, the source told Logan.

The defense team had to know that much about Seddique before the trial started, even if they didn’t know he’d been an FBI informant. But what was the FBI thinking in connecting itself to a seemingly Taliban-friendly nutcase in the first place, and how did they miss his money transfers during their relationship? Could they have discovered Omar’s radicalization earlier by paying attention to the father more?

I’d bet those are questions that Salman’s defense team would have looooved to pose to prosecution witnesses on cross-examination. And I’d bet that they get another chance — and another trial — in which to do so.

Update: The trial continued this morning, and the defense pounced on the FBI. Krista Torralva, a reporter with the Orlando Sentinel, reports that FBI agent Juvenal Martin testified that the bureau considered developing Omar Mateen as a separate source, and were informed that Omar had made repeated threats and bragged about his connections to al-Qaeda and the Muslim Brotherhood:

Just how much did the FBI know — and how much did they deliberately overlook? Martin’s testimony does establish that Salman was present for all three interactions between the FBI and her husband, which isn’t exactly a boon to the defense, but this raises all sorts of questions about the FBI’s actions previous to the Pulse massacre.

Update: The Orlando Sentinel now has these developments in its updates on the trial. The judge has put off consideration of the mistrial motion until after Martin testifies:

“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,” attorney Fritz Scheller argued in the court filing.

U.S. District Judge Paul Byron said he would consider the motion later today.

“I’m not going to address it right now,” he said. “It’s gonna take too much time.”

Martin’s testimony as to the FBI’s knowledge of Omar Mateen’s threats could make a mistrial even more likely.