Understanding “Exculpatory Evidence” in a Criminal Defense Case

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Exculpatory evidence includes any evidence that may prove a defendant’s innocence.

Examples of exculpatory evidence include an alibi, such as witness testimony that a defendant was somewhere else when the crime occurred.

Exculpatory evidence might include proof that the defendant stayed in a hotel too far away from the crime scene to have committed the crime.

Better yet, perhaps the defendant visited a bar, and the bartender on duty that night was found and questioned.

If you have questions about exculpatory evidence in California, please contact or call (619) 439-0981 to reach the San Diego defense lawyers at the Law Offices of Kerry L. Armstrong, APLC today to schedule a confidential consultation.

Why Is Exculpatory Evidence Important?

Exculpatory evidence is important in a criminal case because it may be the difference between a person walking free or spending time in prison.

A person should face criminal punishment only if they commit a crime. In previous cases in the United States, innocent people were punished because the prosecution did not share key information that proved the defendant’s innocence.

As a result, laws have changed to help ensure that the justice system punishes only people who commit a crime.

Prosecutors are now required to share any exculpatory evidence that may prove a defendant’s innocence. This requirement ensures fairness in our criminal justice system.

Offense vs Defense in a Trial

In the United States, a defendant is presumed innocent unless proven guilty beyond a reasonable doubt.

The prosecutor must find extremely strong and powerful evidence showing that the defendant committed the crime.

Strong and powerful evidence can refer to one or more eyewitnesses or DNA testing of crime scene evidence to prove that the defendant was at the scene of the crime.

If the prosecutor finds evidence that shows the defendant was somewhere else at the time of the crime, then the prosecutor must turn that evidence over to the defense attorney and the defendant.

If the prosecutor fails to turn over the evidence and the defendant is found guilty, that conviction and subsequent sentence can be overturned.

Failure to provide new evidence showing a defendant’s innocence is called a miscarriage of justice.

Example: Brady v. Maryland (1963)

The Brady v. Maryland case of 1963 concerned a defendant in a criminal trial who was convicted of murder and was sentenced to prison.

The prosecutor had information showing that another prisoner, Brady’s accomplice, had already confessed to the murder.

The prosecutor did not turn over that information to the defense team or the court.

Therefore, the jury convicted Brady and found him eligible for the death penalty.

If they had heard the new evidence, then they may have decided differently on the outcome.

The suppression of the evidence denied the defendant his due process of law, which goes against the United States Constitution and Bill of Rights.

Brady Material or the Brady Rule

Exculpatory evidence is also called Brady material and includes any evidence that may prove a defendant’s innocence.

The Brady Rule requires the prosecutor to turn over exculpatory evidence to the defense team before trial.

However, the defendant must prove that the evidence will help their case.

For example, the defendant can show that the evidence:

  • Proves their innocence,
  • Could reduce their sentence, or
  • Discredits one of the prosecution’s witnesses.

The Brady rule helps protect the defendant’s right to a fair trial. 

What Happens If There Is a Brady Violation?

The U.S. Supreme Court ruled that Brady violations constitute a violation of a person’s right to due process.

Due process rights are protected by the U.S. Constitution and include things like:

  • The right to have an attorney,
  • The right to a trial by jury,
  • The right to notice of criminal charges, and
  • The right to face your accuser.

If a court finds that a Brady violation occurred, the court must reverse the defendant’s conviction and order a new trial.

In some cases where a prosecutor deliberately withholds exculpatory evidence, a court may punish or sanction the prosecutor.

What Is a Giglio Violation?

In 1972, the U.S. Supreme Court issued a decision in a case called Giglio v. United States. In that case, the prosecution promised a witness that he would not face criminal charges if he agreed to testify against the defendant, John Giglio.

The prosecution did not inform the defendant or his attorney of their agreement with the witness. The witness’s testimony resulted in Giglio’s indictment and later his conviction and sentence to five years in prison.

In its decision, the Supreme Court ruled that exculpatory evidence included any negotiations or deals between the prosecution and witnesses in a criminal case.

Even if unintentional, if the prosecution withholds any evidence that might prove a defendant’s guilt, the court must grant a new trial.

Today, a Giglio violation occurs if the prosecution negotiates with a witness and fails to inform the defendant of the deal. Giglio’s violations require the court to call for a new trial.

The Perry Mason Effect

Some crime show fans may remember the Perry Mason series that ran for many years. Perry Mason always successfully uncovered the criminal who committed the crime. And often, Perry Mason proved that the person on trial was innocent.

During some episodes, Perry would discover a flaw in the evidence against his client. He might discover that the evidence proved that one of the witnesses committed the crime.

Through Perry’s expert questioning of the witness, he could trick the witness during trial and force them to confess to the crime. His client, the defendant, was now free.

Do You Have Questions About Exculpatory Evidence?

We, too, are committed to uncovering the truth and providing a strong defense. The criminal defense attorneys at The Law Offices of Kerry L. Armstrong, APLC, put our client’s interests first.

With experience in well over 100 jury trials, we provide each client with personalized legal services backed by extensive courtroom experience and legal knowledge.

If you have been charged with a crime and need help, call us at once at (619) 439-0981 or fill out an online form for a free consultation. We can help you.

Author Photo

Kerry L. Armstrong


Attorney Kerry Armstrong opened up his law firm in June 2007. Mr. Armstrong attended Thomas Jefferson School of Law, San Diego, California, and received his B.S. from Middle Tennessee State University. Kerry L. Armstrong became certified by the State Bar of California’s Board of Legal Specialization for criminal law in August 2020, making him one of the few criminal defense attorneys with a criminal law legal specialization certificate in San Diego County.  Between 2014 – 2019, Mr. Armstrong was selected for inclusion in the California Super Lawyers list, an honor only awarded to 5% of the nation’s attorneys.

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