Who KILLED Bruce Wayne?!

As an old friend of Bruce Wayne, you are invited to a party. You arrive to the party and, lo and behold, only people who know Bruce is Batman are there. You begin to talk to the party-goers, some of which you haven't seen in years. As the party dies down, suddenly, Bruce Wayne mysteriously faints and dies! His wine had been poisoned by someone who was out to get him. Who did it? You must find out.