Robert Durst

And he talks to himself.

His face would twitch and he would blink.

You had to really look at and figure out how much was true and how much wasn't.

Now, Jarecki and Smerling have all this footage, 20 hours of interviews with Bob Durst.

The next objective is to get friends and family and associates to tell their part of the story.

That was not going to be an easy task.

In fact, it took four years.

In 2011, we start doing interviews.

One of the interviews is Sarah Kaufman, who is Susan Berman's, he's not adopted by Susan, but might as well been adopted son.

I stayed in L.A.

to keep doing some research, and Saurabh called me the next day, and he said he'd filed something.

He said, can you come by?

And I said, sure.

So you can see in the jinx, I go by, and Saurabh shows me this letter.

And the writing on the letter is identical, almost, to the writing on this cadaver note that had been sent to the Beverly Hills Police Department after Susan was murdered.

We fly back to New York, we put in a safe deposit box, and we sit down and we go, oh my God, what are we gonna do next?

We realized we had something that was evidence in a murder trial.

Every documentary filmmaker hopes to find that golden nugget, that unique thing that blows the project wide open.

They could never have imagined what was about to happen.

They take these two identical envelopes and plan to show them to Bob Durst with camera rolling.