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Cannon's career began back to the 1950s with roles in shows like Alfred Hitchcock Presents, The Outer Limits and Combat!. On Magnum, P.I., Cannon was featured as Dr. Ibold, while on Hawaii Five-O, he played Attorney General John Manicote.
In recent years, he served as president of the Hawaii chapter of the Screen Actors Guild and its successor group, SAG-AFTRA.
He was a Professor of Theatre at the University of Hawaii at Manoa and also co-Director of the UH-Manoa Cinematic and Digital Arts program.