Definition - What does Not Guilty mean?
The term not guilty refers to the plea of a defendant who is accused of a crime, which they believe they have not committed when brought forward to the judge initially.
Justipedia explains Not Guilty
The choices that defendant has in this case are usually these – guilty, not guilty, not guilty due to insanity, no contest, or unable to stand trial. If the person accused is proved insane at the time of the crime, they will be ruled not guilty and can’t be prosecuted for the same crime again.