Sean Baker’s review published on Letterboxd :
Cool film. Easily one of the best US films of the year. Love the hybrid docu/fiction nature of the film. Lots to analyze here... because basically this is a documentary with cinematic reenactments.
From imdb: During filming the actors were not allowed to meet their real life counterparts because the director feared they would sympathise and/or play them in a certain light.
The director originally approached Warren and the others about the film while they were still incarcerated for the crime. The resulting relationship that developed culminated in the final film, after they were released.