Robert Durst Finally Locked Up in L.A. Jail

Robert Durst has been extradited and is now in an L.A. County jail, awaiting a court hearing where he will be arraigned on the charge of first degree murder in the death of Susan Berman ... TMZ has learned.

Durst was the subject of the docuseries 'The Jinx,' where he made a statement some say was incriminating and others say a downright confession when he uttered the words, "killed them all."

Berman was murdered in 2000, and authorities believe Durst killed her because she knew something about the mysterious death of his wife, Kathleen, who disappeared in 1982.

We've learned Durst will plead not guilty to the charge when he is arraigned in L.A. Superior Court on Monday.

He has a powerful, multi-state legal team, which includes Dick DeGuerin, Chip Lewis, David Chesnoff and Don Re ... all of whom have won big murder cases.

We've learned he was taken from an Indiana federal prison to L.A. County jail, where he will await his court appearance.

Durst is being held without bail.