Discovery is the general process of a defendant obtaining information possessed by a prosecutor regarding the defendant's case. In addition, prosecutors may be allowed to obtain all information a defendant holds regarding a case as well. This inter-exchange of information is commonly known as the "discovery period", which typically occurs prior to trial, but as evidences surfaces, may extend well into a given trial period. Typically, discovery periods involve the exchange of any information or evidence a prosecutor intends to use against a defendant during trial, which may include:
The distinguishing characteristic between "raw evidence" and other information potentially coming out from a prosecutor's office is that the evidence is presented as is. In essence, a defendant will receive all potential evidence, but they are not required to receive any information regarding the prosecution's intention to admit this evidence, or how this evidence may play into their overall legal strategy.
The intention of the discovery period is a two-pronged attempt by the courts to better the criminal justice process. First, as most would assume, discovery allows a defendant a better chance, or fairer chance, during trial. Contrary to popular crime dramas, surprise evidence at the last minute vindicating or convicting a defendant is rare. Additionally, by providing all evidence against a defendant, the defendant may prove more likely to agree to a plea agreement, sparing both the prosecutor's office and the courts the burden of going to trial. Included in most reciprocal discovery periods include pieces of evidence and reports, such as arrest warrants, search warrants, grand jury indictment testimony, police reports, and previous arrest records.
In order to facilitate fairness, the laws provide that prosecutors provide the defense with any evidence that may potentially benefit defendants as well during the discovery period. This exculpatory evidence may help establish a defendant's innocence, and if not turned over, can result in the overturning of any conviction upon appeal. Typically, any information that may present any doubt concerning the guilt of a defendant, according to a reasonable juror, is deemed exculpatory evidence in most cases. To force the turnover of this information, defense attorneys usually make their requests from the onset, as well as interviewing other parties that might be aware of the existence of exculpatory evidence, such as directly interviewing police officers, other attorneys, and witnesses in the case both before and after a trial.
Due to reciprocal discovery laws at the federal and state level, the defense is required to share certain information with the prosecutor's office as well. This information may be restricted successfully through Fifth Amendment claims, but for federal courts, a request to produce an alibi to the defense means that the names corroborating this alibi must be provided. Some states include more comprehensive reciprocal evidence rules, which vary from jurisdiction to jurisdiction.