Genre research - Detective and Mystery

I have been researching different film genres to try and help me decide which genre I am going to use for my final AS piece.
One film genre I am considering using is Detective and Mystery. Films in this genre include:

• Alfred Hitchcock's Rear Window

• Alfred Hitchcock's Vertigo

• Roman Polanski's China Town

Detective - mystery  films are usually considered a sub-genre of crime/gangster films that focus on unsolved crime. They emphasize the detective or person (usually an ordinary, plain-clothed policeman or detective) solving the crime through clues and exceptional rational powers. The detective studies the intriguing reasons and events leading to the crime, and eventually determines the identity of the villain (a murderer, a master spy, an arch fiend, an unseen evil, or a malignant psychological force). The central character usually explores the unsolved crime, unmasks the perpetrator, and puts an end to the effects of the villainy.
Suspense is added as the protagonist struggles within the puzzle-like narrative to gather evidence and testimony, to investigate all motives, and to discover the one essential clue or fatal flaw/alibi that betrays the identity of the culprit. The detective (or main protagonist) often succeeds in cleverly trapping the killer or criminal where law-and-order officers and local police officials do not. Intensity, anxiety, and suspense build to an exciting climax, often with the detective (or protagonist) using his fists or gun to solve the crime.

If I used this genre, I would be keen to introduce a likable, sort of innocent character to whom people would be able to relate to as the detective/policeman. I believe this would engage the viewers, and make it a more effective opening. This is used in Hitchcock's Rear Window as the viewers are positioned with the policeman/detective, which allows them to get to know the character, and then allows them to sympathies with him when the film comes to its famous climax.