He narrates his troubled life story to the camera, behind which Clarke and her partner at the time, actor Carl Lee, provoke and berate Jason with increasing hostility as the film progresses.

The film employs avant-garde and cinéma vérité techniques to expose the tragedy underlying Jason's theatrical, exaggerated persona.

[4] While Clarke originally intended for Jason to be the only speaking character in the film, she included the off-screen voices of her, Carl Lee, and other crew members in the final cut.

[4]The inclusion of the off-camera voices is most important in the final reel, when Carl Lee and others begin to verbally attack Jason for wrongs he has done them or their perception of his bad character.

Upon its 1967 release, Bosley Crowther of The New York Times admired Portrait of Jason as a "curious and fascinating example of cinéma vérité, all the ramifications of which cannot be immediately known.

The website's critics consensus reads: "Like any great work of art, Portrait of Jason tells a story that reaches far beyond its canvas in the act of illuminating its subject.

"[12] Documentary filmmaker Connie Field assessed the film quite negatively: I felt [Clarke] was exploiting him ... not because ... of trying to reveal a person at all.