William L. Prosser

William L. Prosser was the most influential American tort law scholar of the 20th century. Often referred to as “Mr. Torts,” his published works fundamentally defined modern concepts of consumer protection, product safety, and personal privacy.

Berkeley Law’s dean for 13 years, he was a driving force in expanding its physical infrastructure, diversifying its curriculum, and elevating its scholarly prestige to an international level. He also established the school’s first Master of Laws (LL.M.) degree program in 1952, which drew generations of talented young lawyers and students from across the globe — greatly enhancing Berkeley Law’s international reach and internal learning environment.

A Marine during World War I, Prosser worked in the public and private sector before entering academia. After serving as Secretary to the United States Commercial Attaché in Brussels and working as an assistant sales manager for a milling company in Minneapolis, he enrolled at the University of Minnesota Law School in 1926. 

Influenced by Supreme Court Justice Oliver Wendell Holmes Jr.’s emphasis on law as a tool for social policy over strict rules, he developed an innovative and robust torts curriculum weaving together case analysis, theory, and practical applications. Revamping the often vague structure of tort law, Prosser presented a clear four-part framework to assess negligence claims: duty, breaching that duty, causation, and actual damage. 

His 1941 Handbook of the Law of Torts quickly became the definitive source on tort law for decades, and over half of U.S. jurisdictions eventually adopted his four-tort model. “His treatise set the template for mid-20th century tort law,” said Berkeley Law Professor Mark Gergen, who teaches Torts.

Analyzing over 300 cases for his groundbreaking 1960 California Law Review article “Privacy,” Prosser clarified the right to privacy and structured it into four distinct torts: intrusion upon seclusion, public disclosure of private facts, false light, and misappropriation of name or likeness. His piece persuaded California courts to use these torts in evaluating duty and causation, and the U.S. Supreme Court validated his approach in major decisions. 

Prosser was the lead reporter on the Restatement (Second) of Torts — an influential treatise published by the American Law Institute often cited by judges — that clarifies and guides U.S. common law regarding torts such as negligence, intentional misconduct, strict liability, and product liability. 

He authored a section greatly expanding strict product liability that served consumer interests, fueling quality control measures and safety warnings and urging standardized tests to distinguish manufacturing flaws from fundamental design defects and inadequate instructions. This helped increase efficiency for production safety and victim recovery.

When Berkeley Law needed a new dean, California Supreme Court Justice Roger Traynor (a former professor and student at the school) was enlisted to “help find someone who would make the kind of splash that would announce to the world that California’s flagship law school would be competing with the old-line institutions of the east,” said Berkeley Law Professor Andrew Bradt. 

Traynor had relied on Prosser’s writings on strict liability in his own groundbreaking opinions on the subject and recruited him from Harvard. “Prosser’s reputation significantly enhanced the law school’s, and its faculty doubled in size during his deanship,” Bradt said. 

As dean from 1948 to 1961, Prosser elevated Berkeley Law’s academic standards, modernized course offerings, and pushed for more interdisciplinary partnerships. The school experienced rapid growth, relocated to a new law building on Bancroft Way in 1951, and broadened its international reach by drawing graduate students from Europe and Asia and bestowing its first LL.M. degrees in 1952. 

Widely credited for transforming Berkeley Law from a regional institution into a global legal education leader, Prosser encouraged teaching practical problem-solving over memorization. In his classes he often used real-world examples, including the Lizzie Borden murder trial, to amplify doctrinal complexities and examine societal implications.

“Although for decades his ubiquitous and authoritative single-volume treatise was known as Prosser on Torts, it was probably more accurate to say Prosser was Torts,” Bradt said. “He was the lead reporter of the Restatement (Second), the author of the most widely used casebook, and the force behind the growth of strict products liability, intentional infliction of emotional distress, invasion of privacy, and more. All these years later he remains synonymous with the field.”

In 1973 the Association of American Law Schools established the William L. Prosser Award, which annually recognizes outstanding contributions to torts scholarship, teaching, and service. 

A larger than life figure, Prosser elicited vivid memories for the school’s 100-year centennial in 2012. Dan Wallace ’63 recalled how he and some classmates frequented a hot dog stand near the law school, regularly crossing paths there with Prosser, and once getting an impromptu lesson on tort law’s assumption of risk concept.

“Professor Prosser came in, got his drink, and proceeded to sit on one of the beat-up high stools that were available — whereupon the chair collapsed, tossing the King of Torts on his derriere,” Wallace said. “Startled by the commotion, we were delighted with his educational response to this situation. He leaped up and announced: ‘Coming in here, I assumed the risk!’ Prosser was not just an excellent teacher, he was inspirational.”

About the Series

The Legends of Berkeley Law series highlights scholars whose ideas helped establish one of the world’s most intellectually influential law schools. Through pathbreaking research, innovative teaching, and institutional leadership, these faculty members reshaped major fields of law and inspired generations of lawyers, judges, policymakers, and academics.