Prosecutors don’t have to actively search for or follow every lead that might lead to information that could help a defendant. But they do have to turn over information that’s favorable to the defense, even if the defense doesn’t ask for it. Defendants are therefore left in the potentially tenuous position of relying on the opposition to help them out, at least to a certain extent. They and their attorneys frequently have the concern (valid or not) that prosecutors have wrongly withheld helpful information. The question is: What, if anything, can they do about it?
Though they have an ethical duty to achieve justice, not just to obtain convictions, prosecutors in an excess of zeal may fail to voluntarily reveal favorable information—that is, information that’s either exculpatory or impeaches the prosecution’s case in some way. Defendants should always be alert to the possibility that exculpatory information exists. Defense counsel may learn of it in one of the following ways:
To defendants’ disappointment, neither they nor their attorneys are entitled to rummage through law enforcement documents and objects in search of favorable evidence. However, defense attorneys can file pretrial motions asking a judge to force a prosecutor to give the defense access to police and prosecution files, or at least to review such files and determine whether the defense is entitled to them. Judges won’t allow defense attorneys to go on “fishing expeditions”—rather, the defense must usually show in advance that there's a good chance the information is subject to discovery.
If you face criminal charges and have an attorney, consult with that lawyer as to how to make sure that the prosecution has turned over all mandated discovery. If you don’t have a lawyer, get one. Only an experienced criminal defense attorney can explain and navigate the ins and outs of the discovery process to make sure you have all the evidence you’re owed.