There are new developments in the murder case involving real estate heir and convicted killer Robert Durst.

Sources tell News 12 that several key witnesses in the grand jury case took the stand Wednesday.

News 12's Tara Rosenblum first broke the news and was at the County Courthouse. Rosenblum confirmed that the grand jurors heard directly from the family members of Robert Durst's missing wife, Kathie, who provided testimony they have waited four decades to deliver.

As News 12 has reported, prosecutors in Westchester first began presenting evidence to the grand jury a week ago in the 1982 disappearance of Kathie Durst in South Salem.

She was 29 when she vanished. Her siblings say she was trapped in a volatile and abusive marriage with the scandalized real estate heir.

Kathie's brother Jim McCormack, her sister Mary Hughes and brother-in-law Tom Hughes all took the stand Wednesday.

While grand jury proceedings are kept secret, News 12 has spoken to all three of them at length about this case and why they believe without a doubt Durst killed their sister.

There are a lot of moving parts with this case, but one unusual aspect is that a state police investigator already filed a murder charge against Durst last week last week, despite the fact the district attorney is in the middle of grand jury proceedings. This could be because Durst is terminally ill and battling COVID-19 and cancer in a California hospital.

Grand jury proceedings are expected to continue Friday.

News 12 reached out to Robert Durst's legal team several times but has not heard back.