The son of Brooke Astor and one of her former lawyers will face felony charges that they induced the late philanthropist to sign off on changes to her will and sold one of her prized possessions, a Childe Hassam painting of Fifth Avenue, without her permission, a source with knowledge of the charges said.

The charges against the son, Anthony Marshall, and the lawyer, Francis Morrissey Jr., were handed up yesterday by a state grand jury and will be made public today. A former CIA agent and ambassador, Mr. Marshall is Astor’s only child. He is expected to surrender to authorities today.

The investigation by the office of the Manhattan district attorney into the dealings of the two men began last year after a public dispute between Mr. Marshall and his son, Philip Marshall, over the level of care that Anthony Marshall was providing to Astor. Philip Marshall accused his father — who had long been Astor’s caretaker — of denying her medical treatment as well as skimping on new nightgowns. None of the allegations were ever substantiated.

Astor died at 105 over the summer, after a court settlement had wrested control over her finances and medical decisions away from Anthony Marshall.

Some of Astor’s favorite charities are fighting with Mr. Marshall in surrogate court over which version of Astor’s oft-changed will to honor. At stake is whether tens of millions of dollars of her fortune will go to her son or to the institutions. Those late-life wills are the focus of the indictment, the source said.

The indictment alleges that Messrs. Marshall and Morrissey engaged in a scheme to defraud Astor, the source said. The indictment focuses on two changes to Astor’s 2002 will made in early 2004. Those amendments gave Mr. Marshall control over how to disburse part of Astor’s fortune that previously had been off-limits to him.

Sorting out whether those changes to the will involved criminal wrongdoing or were simply the routine transfers of wealth from one generation to the next will require a trial.

The New York Times has reported that Astor’s signature on the third codicil, as the amendments to the will are known, may have been a forgery. It is unclear whether the indictment claims the signature was a forgery. The indictment, a source said, alleges that Messrs. Marshall and Morrissey induced Astor to make the changes. In the years before her death, Astor’s mental health was slipping, although its unclear at what point she could no longer manage her finances on her own.

The source said the indictment also charges the two men for their alleged role in the sale of the iconic Hassam painting, “Flags, Fifth Avenue,” which Anthony Marshall sold in 2002.

Lawyers for Messrs. Marshall and Morrissey, and a spokesman for the district attorney, did not return calls for comment.