As you play through Detective Pikachu, you will need to solve a number of cases. In order to do this, you will first have to scour the surrounding area in search of both Clues and Eyewitness Testimony. After obtaining all the information you will need to solve a case, all you must do is simply go into your Case Notes in order to put all the pieces together. After doing so, Tim will usually identify the culprit, which will see them be apprehended for their crimes.