New York real estate heir Robert Durst, who days ago was sentenced in a two-decade-old murder case, has been hospitalised after contracting COVID-19, his lawyer said.

Defence attorney Dick DeGuerin said he was notified Durst was admitted after testing positive for the coronavirus. Mr DeGuerin told multiple media outlets Durst is on a ventilator. Additional details on his condition were not immediately made available.

The Los Angeles Superior Court said in a statement Saturday the court was notified someone present for the sentencing hearing for Durst on Thursday had tested positive for COVID-19.

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"As a result, the Court will follow CDC and LA County Department of Public Health guidelines for assessing close contacts of the infected individual," the statement read.

No additional COVID-19 cases have been reported.

Durst, 78, was sentenced Thursday to life in prison without a chance of parole for the murder of his best friend more than two decades ago.

Durst, who has numerous medical issues, sat in a wheelchair with a catatonic stare during much of the sentencing hearing.

"He was very, very sick in the courtroom," Mr DeGuerin said Saturday.

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He was convicted in Los Angeles Superior Court last month of first-degree murder for shooting Susan Berman point-blank in the back of the head at her home in December 2000.

The killing had been a mystery that haunted family and friends for 15 years before Durst was arrested in 2015 following his unwise decision to participate in a documentary that unearthed new evidence and caught him in a stunning confession.

Mr DeGuerin said Thursday that Durst will appeal.