Note that the US does not have a single definition of murder; there are loose common guidelines, but each jurisdiction within the U.S. has its own, slightly different, definition of each form of murder. The specific statutes matter a lot in actual cases even if they get ignored in general discussion, as do the actual charges filed. The fact that another form of murder exists that could have been supported based on the trial evidence will not save a conviction on appeal if the appellate court feels the evidence cannot reasonably support a conviction for the specific form of murder actually charged.