NEW YORK - After four months of testimony that cast a harsh light on the operatic lives of East Coast social royalty with tales of greed, abuse and family feuds, a jury on Thursday convicted the son of legendary philanthropist Brooke Astor of tricking her into changing her will.

The jury, which deliberated for 11 days, found Anthony Marshall guilty on 14 of the 16 counts against him, including grand larceny involving the theft of cash and art, possession of stolen property and conspiracy to defraud Astor.

The philanthropist, who died in 2007 at age 105, was known for her lavish donations to New York's most venerable institutions, including the Metropolitan Museum of Art and the New York Public Library, as well as universities and hospitals.

Estate attorney Francis Morrissey was convicted of all five counts against him, the most serious of them forgery for allegedly altering Astor's will to divert her nearly $200 million fortune to her son. He faces up to seven years in prison, while Marshall, 85, could receive up to 25 years.

Marshall, a Tony Award-winning Broadway producer and former U.S. diplomat, sat stonelike as the jury forewoman read each verdict aloud.

States of confusion

The prosecution had presented a gargantuan case that included 72 witnesses but was based largely on circumstantial evidence.

Most of the witnesses, who included Barbara Walters and Nancy Kissinger, could not testify as to Astor's mental condition during the precise moments when she signed changes to her will.

Instead, they recalled moments when they had seen her in apparent states of confusion, a result of the Alzheimer's disease she was diagnosed with in January 2001. They recounted lavish dinner parties at which Astor could not recognize close friends and instances in which she displayed irrational fears or erratic behavior.

Prosecutors said Morrissey and Marshall took advantage of Astor's diminished mental state to coerce her to change her will and give Marshall proceeds from sales of valuable artwork. Their witnesses included Astor's former butler, chauffeur, maids and nurses who tended to her needs at her Park Avenue apartment, her seaside home in Maine and her estate in Westchester County, north of New York City.

The defense, which called just two witnesses, said none of that mattered and that jurors should focus only on Astor's mental state during the brief meetings she had with lawyers to amend her will in 2003 and 2004.

Changing her will to give money to Marshall rather than to her favorite charities was simply the result of a mother wanting to show love for her son and reward him for decades of loyalty, defense lawyer Frederick Hafetz said in his closing arguments.

"The one enduring relationship in her life was Tony," Hafetz told the jury.

But Marshall's son, Philip, told a different story. In 2006, he accused his father of letting Astor live in squalor -- which prompted a judge to remove Anthony Marshall as her legal caretaker.