"How could I have known that murder can sometimes smell like honeysuckle?". This line is from which Hollywood movie?

As part of the dialogue which is used by Walter Neff (a smart and clever insurance salesman), he specifically says, "It was a hot afternoon, and I can still remember the smell of honeysuckle all along that street. How could I have known that murder can sometimes smell like honeysuckle?"

Here, in this 1944 film, Double Indemnity by Billy Wilder is a cynical, witty, and sleazy crime thriller (drama) about a smooth-talking salesman and his lover who conspire to kill her husband. Murder is under consideration, so they talk about smells, cars, time tables, etc. They absolutely need to make it look like an accident so that the wife can claim money from a life insurance policy. The only obstacle in the plan is the salesman’s boss, an expert at detecting false insurance claims.

Therefore, is it possible that anyone could at any point in time honestly think that the wrongdoers (crooks) in these circumstances could come up with a fail-safe murder plan and totally get away with it? Double Indemnity provides an answer.