When it comes to criminal trials, law enforcement agencies are required to collect and preserve certain material evidences that are directly related to the facts and issues of the case. Apart from the officials of the investigative agencies, those working under the prosecutor must also exercise due care, while handling such evidence. The duty to preserve the evidence does not end with a conviction, as it extends to the officials of the Attorney General's office, which is responsible for appeals. While the law enforcement agencies have to preserve the evidence, the prosecution has the duty to disclose material evidence to the accused. Evidence that is favorable to the prosecution is called inculpatory evidence, and they indicate the involvement of the accused in the crime. There is another set of evidence that is favorable to the accused, and it is called exculpatory evidence. According to the constitutional due process, the prosecution has to disclose both exculpatory and inculpatory evidence to the defense counsel. So, evidence favorable to the accused in a criminal trial is called exculpatory evidence. Such an evidence may indicate that the accused is not guilty, or justify his act. The prosecution has to disclose the evidence to the defense, even if the latter did not request for the same. The legal definition of exculpatory evidence is as follows: Evidence, such as a statement, tending to excuse, justify, or absolve the alleged fault or guilt of a defendant. Given below are some examples of exculpatory evidence. Example 1: The prosecution has a CCTV footage from the crime scene, that shows someone else committing the crime. This is a material evidence that shows that the accused is not guilty. The CCTV footage is an exculpatory evidence in this case. Example 2: In a murder case, a man was arrested from the crime scene along with a blood-stained knife. According to the suspect, he was trying to help the victim, by taking out the knife. During investigation, an eye witness identifies another man as the murderer. The testimony of this witness is exculpatory evidence, that must be disclosed to the accused, so that he can prove his innocence. Example 3: DNA or fingerprint evidence not matching with the accused is also an exculpatory evidence that has to be disclosed to the defense counsel. Such evidence can play a major role in the outcome of the case. In short, evidence collected from the crime scene, forensic analysis reports, investigative notes and recordings of statements (audio or video), etc., are considered exculpatory evidence. The prosecution must disclose the evidence to the defense, even if it is not so solid. Brady v. Maryland, 373 U.S. 83 (1963) is one of the significant judgments delivered by the Supreme Court of the United States. The petitioner and his companion (named Donald Boblit) were sentenced to death for committing first-degree murder. Though Brady admitted that he was involved in the crime, he claimed that the act of killing was done by Boblit. Brady's counsel had requested access to all material evidence, including Boblit's statements. Though most of them were provided, the prosecution had some evidence that was not shown to the petitioner's counsel. They included Boblit's written statement admitting that the actual killing was done by himself. Brady's counsel appealed before the Maryland Court of Appeals for post-conviction relief. During the post-conviction proceedings, Brady's counsel raised the issue of Boblit's written statement that was not disclosed by the prosecution during the trial. The appellate court held that suppression of evidence by the prosecution is violation of due process clause. The court ordered new proceedings for deciding the sentence. Eventually, the case reached the Supreme Court. The Supreme Court upheld the judgment of the Maryland Court of Appeals and ruled that the action of the prosecution violated the due process rights of the petitioner. Nowadays, the ruling in Brady's case is widely applied; and exculpatory evidence is often called Brady material. The scope of Brady rule widened further with successive judgments. In Giglio v. United States, 405 U.S. 150 (1972), the court ruled that exculpatory evidence included impeachment evidence too. In United States v. Agurs, 427 U.S. 97 (1976), the court held that exculpatory evidence must be disclosed to the defense, even if there is no request from the latter. In United States v. Williams, 504 US 36 (1992), the Supreme Court ruled that the suspect has no right to present, and the grand jury has no obligation to consider, exculpatory evidence; it would be incompatible with the traditional system to impose upon the prosecutor a legal obligation to present such evidence. If the defense claims that the prosecution has withheld some material evidence, the burden of proof lies with the former. The defense has to prove that the suppressed evidence was so important that it would have altered the outcome of the trial, had it been disclosed earlier. The burden of proof lies with the defense, who claims that exculpatory evidence has been destroyed by the prosecution. It is really difficult to prove this claim, unless the evidence in question is one that is normally preserved in any criminal litigation. Failure on part of the prosecution to disclose exculpatory evidence may lead to dismissal of the case, reversal of conviction on appeal, or an order for a new trial. In other words, the defense may opt for a motion for dismissal or appeal against the conviction. They may also move the court for a new trial. The importance of exculpatory evidence during trial has been upheld by various judgments. What about application of Brady rule after conviction? What if the prosecution comes up with some exculpatory evidence after conviction? Though there is no provision for disclosing such evidence after conviction, it has always been contended that it is ethical for the prosecutor to inform the appropriate authority as well as the convicted defendant. In short, Brady rule speaks about the prosecutor's duty regarding exculpatory evidence. Though the law enforcement agencies are not required to search for exculpatory evidence; the prosecution should not suppress the same, if there is any. Even though an exculpatory evidence weakens the prosecution case, it is unethical to suppress such evidence.