I think that anyone that has watched the series leaves with the opinion that this guy is a cold blooded killer. Very narcassistic behaviors. Manipulator. Liar. Etc...
But unless the LA/Beverley (ha) Hills police have actual forensic evidence, I don't see a conviction. Yes, the documentary probably tainted people views and probably towards the truth, but he has the best lawyers in the county.
He actually can create very logical explanations for the evidence. He was on the run because he wanted to avoid the public scrutiny. He will admit to writing the letter and state that he stumbled upon the body in LA after wanting to visit a friend, found her dead, panicked because he believed the police would connect the dots to his "missing" wife. His attorney will argue that just because he wrote a letter, does not mean he murdered Barbara.
As for the "confession" his lawyers will fight to keep that out of court because it occurred in the bathroom. From my law classes at Pitt, I seemed to recall something about not being able to tape in private restrooms. But lets say that it is allowed in court. His lawyers will simply argue that it wasn't a confession, but an internal monolouge that Durst was having with himself and he was just logically stating what the viewing audience was thinking of him. It wasn't a confession, but just his thoughts coming around to how he looked.
Now again, I think the viewers will say this guy did it. Too many coincidences of people he knew being killed. But unless the police have better forensic evidence somewhere, or a hand written note that wasn't shown on TV telling somehow how he did it, (a sort of OJ "If I did it" moment) I just don't see him seeing jail time.
Finally, I have attached a New York Times article discussing how the film's producers went through their own legal struggle with what to do with the evidence. Based upon the article, it appears that they properly handled the evidence, so I will withdraw my previous statement questing Jareki's morals and journalistic ethics.
I hope HBO not only covers this trial, but has a least an hour special discussing how their film work lead to this arrest. I liked the show, but to say that the story has been told would be incorrect....
http://www.nytimes.com/2015/03/16/nyregion/robert-durst-subject-of-hbo-documentary-on-unsolved-killings-is-arrested.html?_r=0