Aside from a so-called accidental confession in an HBO docuseries, Robert Durst's attorneys will have to explain another incriminating piece of evidence. 

Durst, 71, was arrested Saturday in New Orleans for the murder of Susan Berman in her Beverly Hills home. Durst waived extradition and will return to L.A. to face trial.

Durst has also been linked to the disappearances of two other people, including his wife in 1982. Berman became a spokesperson for Durst and was murdered just days before police were going to interview her about Kathie Durst's disappearance.

In the finale that aired Sunday night, Durst could be heard mumbling on a hot mic, "What the hell did I do? Killed them all, of course."

In the interview, Durst was also challenged on a handwritten note that was sent to Beverly Hills Police at the time.

The anonymous letter told police they would find "a cadaver" in Berman's home.

The handwriting in the letter bears a striking similarity to an envelope previously sent to Berman by Durst.

Both letters were written in block handwriting and the writer misspelled Beverly Hills as "Beverley" on both occasions.

Judge Andrew Napolitano was asked this morning about this new piece of evidence against Durst. He called the handwriting similarity the "most damning" piece of evidence. 

He predicted that the defense will call experts to the stand to try to "explain it away," probably arguing that "Beverley" is a common misspelling.