It is going to be a rare look inside New York's high society as trial begins for the son of one of New York City's wealthiest women.
But in her opening statements, prosecutor Elizabeth Loewy said Marshall and his lawyer took advantage of his mother's Alzheimer's Disease.
"The defendants exploited Brooke Astor's diminished mental capacity and abused Marshall's power of attorney to enrich themselves," she said.
Brooke Astor died at the age of 105 in 2007. Marshall will be 85 next month.
Prosecutors said Marshall and his lawyer re-routed money meant for New York City non-profits like the Public Library and the Fresh Air Fund.
Marshall hoped "to redirect millions from charities to line their own pockets," Loewy said.
But Marshall said he had his mother's best interests at heart, and that the grand dame of New York philanthropy was of sound mind when she directed him to change her will.
Jurors will decided for themselves, at some point helped by the testimony of people like Barbara Walters and Henry Kissinger, who are expected to testify at the trial.
Defense attorneys will make their opening remarks on Tuesday.