Where a defendant is added in an amended complaint, whether the amended complaint relates back to the original depends on whether the new defendant knew or should have known that the plaintiff erred in excluding him as a party in the original complaint.The 1st District Appellate Court answered two certified questions from the court of Cook County Associate Judge Moira Susan Johnson.On Sept. 10, 2011, Stefan Zlatev was involved in a fight starting in an apartment building and spilling out onto the street. During the fight …