In fact, by the time they arrest someone with reasonable suspicion, there is an 80% chance that the suspect is the culprit. Therefore, beyond any reasonable doubt, a blurred line is established. The investigators have evidence to arrest the suspect, convincing him to confess becomes the mission of the case. Whether they are innocent or guilty or not does not matter, because it is likely that their suspect is actually guilty. And the faster they arrest someone, the better their arrest record becomes and the further they can advance in their career. If that means overlooking some information and just aiming to get the confession, to get an arrest, he will do it