WHAT HAVE I MISSED?

Shouldn't it be a simple matter? Wasn't there physical evidence left on the victim? Can't they simply wait for the DNA results and then know that they have or don't have the right assailant? What is all this speculation and wasted news time about? It should be as easy as 1-2-3. The first step (1) is he admits he is guilty. The second step, (2) we get his DNA and check it against the evidence at the scene. The third step, (3) we put the crazy "proven" guilty man on trial or we send the crazy crazy "lying" man to a hospital for the insane..........