A more thorough explanation:

The Brady rule is a legal requirement that prosecutors must disclose any material, exculpatory information in their possession to the defense. This rule is named after the case Brady v. Maryland. The information that prosecutors must disclose is called Brady material. It includes any information that could help the defendant's case, such as evidence that could reduce their sentence or discredit an unfavorable witness.

Initially, the Brady rule only applied if the defendant requested specific information that the prosecution denied. However, in United States v. Bagley, the Supreme Court eliminated this requirement and stated that the prosecution has a constitutional duty to disclose all material, favorable information in their possession to defendants regardless of whether it is requested. This duty is breached regardless of whether that information is withheld intentionally or unintentionally.

If a Brady rule violation is discovered during trial, the court can either declare a mistrial or prohibit the prosecution from using unfavorable evidence that could be discredited by the withheld information. However, violations of the Brady rule are typically only discovered after the defendant is already convicted. As a result, the most common outcome of a Brady rule violation is overturning that conviction. Additionally, if the prosecution withheld Brady material intentionally or knowingly, they may be subject to sanctions.

The defendant bears the burden to prove that any withheld information was both material and favorable. A defendant meets this burden if they can show that there is a reasonable probability that the outcome of the trial would have been different had the information been disclosed.

Example 1: A prosecutor is handling a case where the defendant is accused of stealing a car. The prosecutor has evidence that the defendant was out of town on the day the car was stolen, but they do not disclose this information to the defense. This is a violation of the Brady rule because the evidence is favorable to the defendant and could have helped their case.

Example 2: In another case, a prosecutor has a witness who claims to have seen the defendant commit the crime. However, the prosecutor also has evidence that the witness has a history of lying under oath. The prosecutor does not disclose this information to the defense. This is a violation of the Brady rule because the evidence could have discredited the witness and helped the defendant's case.

These examples illustrate how the Brady rule requires prosecutors to disclose any information that could help the defendant's case. If the prosecution withholds this information, it can be a violation of the defendant's constitutional rights and can lead to a mistrial or overturned conviction.