Petit jury - a trial jury, which weighs the evidence against someone accused of a crime, and determines his or her guilt or lack of guilt under the law. Trial or petit juries traditionally have 12 people, although several states have juries with only 6 people. In most states, all the members of the jury must make their decision on the person's guilt or lack of guilt (verdict) unanimously. Some states, however, only require a majority which is greater than a simple majority. If a jury cannot agree on verdict, it is declared a "hung jury," and the matter is either dropped or brought to another trial with a new jury..