What is discovery in a criminal case and how does it work into a case?

The simplest explanation of what discovery is in a criminal case is what information each side owes the other before a trial begins. The purposes of discovery is to allow both sides to prepare for trial and prevent a trial proceeding where one side ambushes the other with information that the other side has no opportunity to comprehend, much less investigate.

Each State has their own discovery rules. The federal courts have their own discovery rules as well. In the State of Illinois, felony cases have rules regarding discovery that were written by the Illinois Supreme Court. If you want to read these rules yourself, they can be found in Illinois Supreme Court Rules 411, 412, 413, 414, 415, and 417.

A link to the text of the rules for the interested reader can be found here:


The main rules that require the most attention by defense lawyers are Rules 412 and 413. Rule 412 discusses what the prosecutors owe the defense lawyer before trial, assuming that the defense lawyer makes a written request (called a Motion for Discovery) for the material.

In sum, it includes a witness list with names and addresses of the witnesses, their statements, and reports that describe their statements. It includes alleged statements taken from the client or a co-defendant, statements made by expert witnesses and their reports.

The prosecutor has to give access to any photographs, videos, or documents that the prosecutor intends to use at trial, as well as any criminal convictions for any of their witnesses.

Illinois Supreme Court Rule 413 is about what the defense owes to the State prior to trial. Among other things, this includes a list of the defense witnesses’ names and addresses and a list of any affirmative defenses the defense may raise (like self defense or alibi). The defense must also give the prosecution access to photographs, documents, and written reports from experts or investigators that the defense wishes to use at trial.

One request a defense lawyer often receives is whether the client or client’s family can have their own copy of the discovery. The answer to this is in Illinois Supreme Court Rule 415 (c) which states that “(a)ny materials furnished to an attorney pursuant to these rules shall remain in his exclusive custody and be used only for the purposes of conducting his side of the case, and shall be subject to such other terms and conditions as the court may provide.”

In other words, your attorney can go over the discovery with the client, as well as show the discovery to the client to help prepare the case, but all copies of the material must remain with the attorney.

If there is something the lawyer believes the prosecution is withholding, it’s up to the defense lawyer to go into court and make an issue of it. The Rules allow either side to go to the judge to settle disputes regarding what has to be turned over and what may remain one side’s secret.

The Law Office of William Wolf, LLC has vast experience with the discovery rules in felony cases, including fighting on behalf of a client to help ensure that no critical information is being withheld from the defense.

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