Born in Winnipeg, Manitoba to Jewish parents who immigrated from Eastern Europe, he received a Bachelor of Commerce in 1962 and an LL.B. in 1966 from the University of Manitoba. Marshall was the only child. His mother, a school teacher, was Russian and his father, a Pole, a bookkeeper and merchant. They met in Canada and settled in Winnipeg, where Marshall was born during the war years. Marshall's father wanted him to be an actuary, and so Marshall pursued a bachelor's degree in commerce at the University of Manitoba, but in his final year he took a course on commercial law and became fascinated by the law and decided on the law as a career path instead.