After obtaining all the evidence during a Case, all the Clues in the forms of Eyewitness Testimonies and tangible proof, you will need to piece the case together with Tim and Pikachu to make sure everything adds up. In order to do this, you will need to go into your case notes and solve the question at hand with the evidence you've collected. After properly doing this, and only after doing this, Tim and Pikachu will either proceed to the next case they must solve or they will point out the culprit they've been seeking.