Prejudice
Judges in a court of law should not be prejudiced when deciding whether someone is guilty. They should have an "open mind" so that they can make a fair decision (this is also known as not having a bias; most judges in a court of law have sworn to be unbiased when deciding a penalty). For example, if that person is the judge's friend then the judge would be prejudiced because he (or she) would not want his (or her) friend to get into trouble. In many other situations it is important not to be prejudiced, such as serving as an adjudicator in a competition or a juror in a trial.