Police films are a subset of crime films. Where crime films focus on the criminals and their actions, police films focus on the legal force in uniform or plain clothes. Their actions are also under scrutiny, legal or not.
To find what we have in the Library's collection, you can do a subject search for "police films" in the online catalog. That search will show you what film titles are classified as police films as well as books and other items about them. As you look at the list under police films, the subject headings which include "history and criticism" talk about the genre itself. The headings which also include a country name are specifically talking about police films in that country.
Articles and other writings about movies can be found in many publications. Our collection does not include a journal or magazine which looks exclusively at police films. Other film journals within our collection will cover police films. You can use Film & Television Literature Index to find relevant articles.