In 1971, justices issued their unanimous Reed vs. Reed decision.
In the opinion, Chief Justice Warren Burger wrote discriminating against someone on gender grounds was the very kind of arbitrary legislative choice forbidden by the the Fourteenth Amendment's Equal Protection Clause.
Historians have called the ruling one of the most important, if overlooked, events of the 20th century.
Derr's client, Sally Reed, was an Idaho woman challenging her estranged husband over which of them should be appointed to oversee their son's estate following his suicide
Derr, who had leukemia, remained humble about the victory, however, saying two years ago: "I was just doing my job."