Definition - What does Bias mean?
Bias is a preconceived idea or belief that guides a person's decision-making in similar matters. Courts will not allow evidence from witnesses who have a bias toward the outcome unless it is as a witness for the prosecution. Similarly, the jury in any case must be made up of people who hold no bias against the person being tried or the subject matter in the case. In this instance, a rape victim would not be able to be on a jury for a rapist, as the belief would be that the victim would have preconceived ideas about the crime and the sentence for the defendant.
Justipedia explains Bias
Bias is something that courts try to control, as the U.S. Constitution allows people to be tried under fair circumstances. Any bias that is brought into a case would be viewed as tampering with the natural outcome of the case.