The purpose of a jury is to ensure a person has as fair of a trial as possible. The jury hears evidence of the case along with arguments from the defense and prosecutor.
After going over the evidence and hearing cases from both sides, the jury has the job of deciding whether or not there is enough evidence to render a guilty verdict. If there is not enough evidence, the jury can hand down a verdict of not guilty. The right to a jury trial is afforded to citizens facing a criminal trial in the Sixth Amendment of the United States Constitution.