The legal definition of Discovery (aka Disclosure), indicates the evidence the prosecution provides the defense on a criminal case. This usually means the police report (aka departmental report, or DR). It can also include pictures of evidence, lab reports, audio or video, etc. The U.S. Constitution requires the prosecutor to tell the defense about each piece of evidence that could be used in the trial. The prosecutor also has the duty to provide any information the prosecutor knows of that might help the defendant. This is one of the best parts of the U.S. criminal justice system. When it works properly.