Photo: Anthony Marshall arrives at Manhattan State Supreme Court for his setencing, Monday, Dec. 21, 2009, in New York.
Defense lawyers have said the former ambassador's illnesses could make any prison term a death sentence.
Marshall was sentenced Monday to the minimum allowed.
The judge gave him 30 days to get his affairs in order.
Photo: Brooke Astor arrives at the play opening of "I Am My Own Wife" Dec. 3, 2003
Marshall also is expected to continue his appeals and might be able to stay free on bail indefinitely.
He tried, but failed, to get the judge to throw out the part of his October conviction that requires prison time.
Photo: Brooke Astor, 95, is seen at the Merchant's House Museum in New York, May 1, 1997.
Marshall was convicted of exploiting Astor's mental frailty to steal from her nearly $200 million fortune. She died at 105 in 2007.
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