There are a fair few with ties to the victim, some more fishy than others. Everyone has a story of their own. Some may even have something to hide. Question anyone. Ask them about any evidence you've collected. And if you think they're lying at any point, call them out using evidence you've collected. You are never limited in where you go. Go anywhere. Follow leads at your pace. Go back to the crime scene. You can't miss anything, as everything is static. This world is a sandbox, and it's yours to investigate and explore as freely as you wish. This isn't some linear narrative. At any point, you can accuse anyone of being the killer. Use the evidence that you've collected, and create a case that proves your suspect is the killer. The killer is somewhere. Don't rule out anyone too easily...