In some cases, at least, it is necessary to work a suicide scene just as carefully as a homicide scene. The reason for this is that, unless the suicide was conducted in the full view of completely reliable witnesses, it is not necessarily clear that a given death really was a suicide.
In some cases, it is clear that a person has committed suicide. When a person stands on a bridge in full view of the public and then jumps, there can be little suspicion of foul play. If a number of witnesses not connected to the witness in any way all see the jump and are all sure that no one pushed the person, then there is no doubt that it was a legitimate suicide.
However, many suicides do not happen like this. Let us imagine that a man goes into his back yard and shoots himself early in the morning when no one is watching. The police cannot be sure that he really committed suicide. Therefore, they will need to work the scene meticulously. They will need to make sure that all the evidence matches what apparently happened. They will need to be completely sure, for example, that the man’s wife did not shoot him and then arrange the scene to make it look like a suicide.
In short, police must not be taken in by the fact that a death looks like a suicide. They must be suspicious so they are not deceived by a clever murderer.