FIlm Noir - Lighting and Its Effects - The Big Sleep Trailer Analysis

The trailer starts off with two characters. One is a woman who seems to be a librarian the other is an detective. The detective give away half the story line as we know there will be a murder later on where he would have to investigate. The hat and mac coat gives away the identity of that specific character. These clothing items are commonly associated with film noir due to the fact it's mostly based on American crime dramas.

In one scene the detective breaks into a house and comes across a dead body. In that scene low key lighting is used. The low key lighting links with the dead body as it creates a mystery about who's killed that person. This raises questions to the audience about why that person perhaps was killed?, who's the killer?, why was he targeted? etc.
In another scene the female character is bent down to the ground looking at something then quickly looks out the door to see if anyone is looking. This also raises question within the audience and suspicion about this character. The facial expersions of her suggest she perhaps is up to no good.