His films included the documentaries Out of Mind, Out of Sight (2014), a film about patients at the Brockville Mental Health Centre, named best Canadian feature documentary at the Hot Docs Canadian International Documentary Festival;[1] NCR: Not Criminally Responsible (2013), exploring the personal impact of the mental disorder defence in Canada;[2] Life with Murder (2010), The Lifer and the Lady and Parole Dance, and the 1986 made-for-television drama Turning to Stone, set in the Prison for Women in Kingston, Ontario.
[3][4] Early in his career, Kastner occasionally took a break from making documentary films on serious topics with lighter fare, which included co-hosting a short-lived children's series for CTV in the early 1980s, Just Kidding, as well as doing comedy segments for the CBC-TV late-night talk show 90 Minutes Live.
[5] In 1986, he produced the dramatic television film Turning to Stone, adapted from some of the interviews with women prisoners he had conducted while making The Parole Dance and The Lifer and the Lady.
[6] A child actor, Kastner's first screenwriting credit came in 1983, when he co-wrote The Terry Fox Story, starring Robert Duvall.
[10] In 2012, he was the subject of a "Focus On" retrospective at the Hot Docs Canadian International Documentary Festival.