Not guilty is a plea entered by a defendant in a criminal or civil case denying blame for the charges brought against him/ her. Not guilty means you deny having done one or more of the elements contained in the offense or that you have a justifiable excuse for doing what you have done. If you plead not guilty the matter will be set for trial at some date in the future.
Not guilty is also a verdict in a criminal trial by a judge sitting without a jury or by a jury after finding that the prosecution has not proved the defendant guilty of a crime beyond a reasonable doubt or that it believes the accused person was insane at the time the crime was committed. The bar against double jeopardy under the U.S. Constitution prevents the defendant from being tried again for the crime charged.