Question: Does the Resolution have to be that the detective finds the killer? Or can the reader find out who the killer is by the 4th driver so that the final act can focus on potentially finding the killers whereabouts and stopping the murderer from committing another murder?
The answer rather depends on what genre you're writing in.
In a murder mystery, the revelation of the killer's identity is usually the final or 5th driver. The reason is that the goal of the story is to discover "who done it." Once that discovery is made, the story is over, except perhaps for showing the aftermath (outcome, judgement).
On the other hand, suspense stories have a goal of escaping from a trap (which the villain sets for the main character). The villain's identity will be hidden for much of the story while he/she lays the trap. The 4th driver will be when the main character realizes the trap is set and who set it, so that the last act becomes a chase as the main character frantically tries to escape. The final driver is the moment when the villain is stopped and the main character decisively escapes.
Thrillers work in a similar way, except that it can be the villain who is trying to escape the main character in the last act. Naturally, the villain usually fails.
So you have to know what genre you are writing and who your audience is.
* People who like an intellectual puzzle (mystery)?
* People who like the anxiety of a slowly building threat (suspense)?
* People who like the adrenaline rush of nonstop action, physical conflict, and a battle of minds (thriller)?
Best of luck