Most of what has been written about Thurgood Marshall, a former United States Supreme Court justice who served from 1967 to 1991, has just focused on his judicial record and on the ideological content of his earlier achievements as a lawyer pursuing civil rights issues in the courts. But when Marshall's career is viewed from a technical perspective, his work with the NAACP (National Association for the Advancement of Colored People) reveals a strategic and methodological legacy to the field of public interest law. Though the NAACP, under Marshall's direction, was not the first legal organization in the U.S. to be driven by a political and social agenda, he and the NAACP developed innovations that forever changed the landscape of public interest law: during the 1940s and 1950s, in their campaign against state-sanctioned racial segregation, Marshall and the NAACP, instead of simply pursuing cases as the opportunity arose, set up a predetermined legal campaign that was meticulously crafted and carefully coordinated.

One aspect of this campaign, the test case strategy, involved sponsoring litigation of tactically chosen cases at the trial court level with careful evaluation of the precedential nuances and potential impact of each decision. This allowed Marshall to try out different approaches and discover which was the best to be used. An essential element in the success of this tactic was the explicit recognition that in a public interest legal campaign, choosing the right plaintiff can mean the difference between success and failure. Marshall carefully selected cases with sympathetic litigants, whose public appeal, credibility, and commitment to the NAACP's goals were unsurpassed.

In addition, Marshall used sociological and psychological statistics—presented in expert testimony, for example, about the psychological impact of enforced segregation—as a means of transforming constitutional law by persuading the courts that certain discriminatory laws produced public harms in violation of constitutional principles. This tactic, while often effective, has been criticized by some legal scholars as a pragmatic attempt to give judges nonlegal material with which to fill gaps in their justifications for decisions where the purely legal principles appear inconclusive.

Since the time of Marshall's work with the NAACP, the number of public interest law firms in the U.S. has grown substantially, and they have widely adopted his combination of strategies for litigation, devoting them to various public purposes. These strategies have been used, for example, in consumer advocacy campaigns and, more recently, by politically conservative public interest lawyers seeking to achieve, through litigation, changes in the law that they have not been able to accomplish in the legislature. If we focus on the particular content of Marshall's goals and successes, it might seem surprising that his work has influenced the quest for such divergent political objectives, but the techniques that he honed—originally considered to be a radical departure from accepted conventions—have become the norm for U.S. public interest litigation today.