You can stream it under the Polish title "Psychika mordercy" .
To watch the documentary (2020) with Polish subtitles ( napisy polskie ), the most reliable method is through a streaming service that officially supports the Polish market. Official Streaming with Polish Subtitles Crazy, Not Insane napisy polskie
As of late 2020, Max officially provides both Polish subtitles and a Polish voice-over (lektor) for this title. You can stream it under the Polish title "Psychika mordercy"