Detective career crime scene evidence left in inventory

After you finish a case are you supposed to get rid of the witness reports and evidence from the previous case that are still left in your inventory? I have found that if you don't do that you don't get prompted to find a new case on the computer for your job assignments. It will just prompt you to add clues to crime map and issue APB without having to even visit the crime scene and I think that's why so many people are having problems finding the suspect or when finding the suspect they don't come back to the police station with you. I think everything has to be done in a specific order to work properly ie get case, go to crime scene, back to police station to analyse evidence, add to crime map, issue APB, find suspect, back to police station with suspect, interrogate suspect, get confession and then put in jail.