Marshall uses computers in all aspects of litigation and court cases. He has tinkered with and assembled electronic gadgets since childhood and worked in the electrical/electronics industry before university. With this life-long interest and experience with computers and his use of it in law, the Chief Justice asked him to sit on the Court of Appeal's first advisory committee overseeing the implementation of technology in Alberta courts. He served on the court technology committee for a decade.

He has spoken on legal matters in New York City, Los Angeles, Toronto, Vancouver, The Banff Centre, Calgary, Edmonton, University of California, University of Alberta, and University of Calgary. His presentations internationally, nationally, and provincially, have included institutional liability for abuse, institutional coercion, trial and appellate advocacy, the effective examination of witnesses, technology and psychology in litigation, and suing big banks. Marshall has a particular interest in acting for victims of institutional coercion inflicted by cults, extreme religions, and interest groups.

He belongs to the American Bar Association and its Litigation Section and the subcommittees on Public Interest, Personal Rights and Commercial Litigation and Business Torts and Human Rights and sits on the executive advisory board of the International Cultic Studies Association . He also belongs to the Association of Trial Lawyers of America and is the first Canadian to be a member of the Association of Business Trial Lawyers of Los Angeles.