Jacalyn M. Duffin CM FRSC (born 1950) is a Canadian medical historian and hematologist.
[1] From 1993 to 1995 she was Associate Dean Undergraduate Studies and Education at Queen's University.
Soon after this, she moved to Paris, where she elected to study hematology and René Laennec at the Sorbonne.
Upon her return to Canada, Duffin settled in Ottawa, where she took on a contract to review a set of slides, which she assumed were to be used in a malpractice suit.
Duffin's testimony was to be used by the Vatican to determine whether Marie-Marguerite d'Youville (1701–1771) had performed a miracle and was worthy of canonization.