Alice is growing because she is slowly coming out of her dream. It is apparent because she has not eaten anything or drank anything. The book does not say what concert the king is referring to. The "evidence" does not seem to be provided for the trial. Perhaps in Wonderland, when there is a trial, no evidence is needed as it is in our world. The rabbit has a horn because it is the instrument used to gather the attention of all the people and creatures who are either part of the trial or onlookers. Everyone wants Alice to leave because she is growing out of control and she keeps knocking things over. She sent the jury flying out of their seats. Although Alice knows nothing about the trial she is questioned because the king does not know that she knows nothing. He calls her up for questioning because he thinks that she either comitted the crime or that she may have had something to do with it.