In losing Lucian Leape to heart failure last 30 June, at the age of 94 years, we lost a rare physician whose insights fundamentally changed how clinicians and the public understand the practice of medicine. His contributions helped transform medicine’s moral self-conception from one that prized perfection and regarded error as a character failure to one that prizes humility and understanding failure. Medical mistakes were his laboratory. They were both his subject and his inspiration. And his career was a study in audacity and late blooming.

He was born on 7 November 1930, in Bellevue, Pennsylvania. His father worked for a steel company. His mother was a schoolteacher. He studied chemistry at Cornell, where he met his wife, Marty. He served in the US Navy, then went to Harvard Medical School, graduating in 1959. He completed general and thoracic surgery residency at Massachusetts General Hospital, then a paediatric surgery fellowship at Boston Children’s Hospital. His first appointment was at the University of Kansas. He helped found the American Pediatric Surgery Association in 1970. He returned to Boston in 1973 as Chief of Pediatric Surgery at Tufts Medical Center.

He had a steady research output, writing just under half of his 200 academic papers and book contributions during his surgical career. He published findings on subjects from child burn treatment to nutritional deficiencies like rickets to paediatric reflux disease. Paediatric surgery was a new speciality, and he was among the pioneers inventing the field as they practised. Several of his papers also show interest in safety from the start. One of his first papers, in 1967, on 148 cases of testicular torsion, was entitled, ‘Invitation to Error’.2 He reported an adverse event in a child who developed calcification of the leg from calcium infusions. He detailed a technique for snaring broken intravenous catheters from the right heart of infants and wrote a series of searing reports on ingestion of lye drain cleaners due to inadequate child safety measures. Preventable injury was already an animating cause.

In 1986, he branched out to do a mid-career fellowship at RAND in epidemiology and health policy. He was hooked, and at the age of 56 years, he made the risky move of departing his chairmanship and full-time practice to become an Adjunct Professor at the Harvard School of Public Health (HSPH). He had been given an opportunity to join an ambitious project to investigate the medical malpractice system, the Harvard Medical Practice Study, which was the brainchild of Howard Hiatt, the former dean of HSPH, and Paul Weiler, a Harvard Law School professor.