Three months into the criminal trial of socialite Brooke Astor’s son, Anthony Marshall, and the lawyer he hired who allegedly helped him loot his mother’s estate, the presiding judge has cleared the way for a trusts and estate expert to testify for the prosecution.

Alexander D. Forger, the former chairman of Milbank, Tweed, Hadley & McCloy, can give expert testimony on the “patterns” of Ms. Astor’s wills and codicils and the “professional practice standards” for trusts and estates attorneys, Acting Supreme Court Justice A. Kirke Bartley Jr. (See Profile) ruled Wednesday from the bench.