The former federal agent who led the FBI's investigation of the September 11th attacks testified in the Etan Patz case Friday, testifying on behalf of accused murderer Pedro Hernandez.

Mary Galligan will arguably be the most credible witness to take the stand in the Etan Patz case.

Galligan was the chief inspector of the FBI. Before that, she headed the Bureau's investigation of the attack by terrorists on September 11, 2001.

One of the first cases she took the lead on, though, was the disappearance of 6-year-old Etan Patz.

Lawyers for the man on trial in the murder case summoned Galligan to testify, hoping to establish reasonable doubt that Pedro Hernandez is guilty. That's because her decade-long investigation focused on another person, Jose Ramos. He is a convicted pedophile who Galligan said told her in 1991 that he picked up a boy in Washington Square Park, and that it could have been Etan.

There's also a map that Galligan's informant claims Ramos made showing the location of the abduction. That informant, Jeffrey Rothschild, was a plant in Ramos' prison cell by Galligan and former federal prosecutor Stuart GraBois, who Ramos hates.

Rothschild testified earlier that Jose Ramos told him: "That bastard (Stuart GraBois) knows I did it.  He can't prove it and it's killing him...We'll both be buried next to 'Eetten.'" Rothschild responded, "Does that mean he's dead?" Jose Ramos: "Of course"

The big problem here, though, is that Rothschild has credibility issues. He's a con man who cheated dozens of Hurricane Katrina victims out of federal aid by stealing their identities. His 40-year-rap sheet also includes multiple convictions for credit card fraud.

Under cross-examination, Rothschild admitted, "There were times in my life where my criminal activity and my court activity were just such a can of worms, I would do anything to untangle them and get a fresh start."

The evidence didn't prove strong enough for criminal charges, but the Patz family sued Ramos, and a judge issued a default civil judgment against him.

The defense expects to rest on Monday with another jailhouse informant. Then, the prosecution will put on rebuttal witnesses.