As you play through Detective Pikachu, you will need to collect what is know as Eyewitness Testimony in order to solve the Case Tim and Pikachu are presently working on. In order to obtain testimonies, all you really must do is talk to all nearby characters, and that includes both people and Pokemon. Furthermore, sometimes you will need to interview some characters possibly twice or three times, depending on what Clues you Find and what other characters might share after first originally talking to someone. By obtaining all the proper testimony and finding all the given clues of an area, Tim and Pikachu will surely solve the case at hand.