What is Exculpatory Evidence? - Definition, Examples & Importance

Instructor: Kenneth Poortvliet
Exculpatory evidence is any evidence in a criminal trial that supports the idea that the defendant is not guilty. In this lesson, we'll discuss what kind of evidence is considered exculpatory, plus examples, and we'll also examine how important it is.

What Does Exculpatory Mean?

A convicted killer is out on parole, and he kills again. Witnesses saw him thrust a knife in his victim and run out of an alley. They positively identified him in a line up, and his DNA is found on the knife. After a guilty verdict, the defense moves to have the verdict set aside because the prosecutor discovered evidence that the killer was still logged in at work when the murder took place. Is that right?

Exculpatory comes from the word exculpate, which comes from two Latin words ex, 'from' and culpa, 'blame'. Exculpatory evidence then, is evidence in a criminal trial that tends to show that the defendant is not guilty. It typically works like this: A defendant is charged with a crime, and both the prosecutor and defense attorney gather evidence to each make their case. If the prosecutor comes across any evidence that tends to show the defendant didn't commit the crime, he or she has to turn it over to the defense. If the prosecutor doesn't, then the case can be dismissed, retried or even the defendant found not guilty.

Which Evidence May Be Exculpatory?

In Brady v. Maryland (1963), the Supreme Court held that exculpatory evidence withheld in a criminal trial can result in a re-hearing of the case. In this case, Brady was convicted for murder, and the prosecutor failed to tell a jury that another defendant, who had committed the murder with Brady, had already confessed to the killing. The court stated that the jury needed to hear that evidence because it could assist them in their decision regarding Brady. From then on, any exculpatory evidence the prosecutor or law enforcement has is called Brady material, the requirement to turn Brady material over to the defense is called the Brady rule.

Any evidence from a crime scene is subject to the Brady rule
crime scene evidence body

But what other kind of evidence is exculpatory? The law says 'any evidence' that tends to show innocence of the defendant is included. This can include crime scene evidence, witness testimony, DNA results, and medical records.

How Exculpatory Must it Be?

If you're a prosecutor or a police detective, how do you know which evidence is exculpatory enough? For example, if the defendant claims he was three hundred miles away during the time of the murder, and he was driving a red 2003 Ford 150 pickup with a front decorative plate that says 'Hog Wild', do you have to turn over all camera images that show a red Ford pickup getting gas or going through a toll booth?

No; in U.S. v. Bagely (1985), the court laid out the legal standard on whether evidence is Brady material. The defense has to show that the inclusion of the evidence might have reasonably resulted in a different outcome. So it wouldn't be reasonable that every red Ford pickup found hundreds of miles away at that time, but what about picture of a red 2003 Ford 150 pickup with a front decorative plate that said 'Hog Wild'? Since it would be reasonable that this would change the outcome of the trial, it would be Brady material.

The Importance of the Brady Rule - An Example

The Supreme Court said that without the rule, the defendant's due process rights would be violated. Due process comes from the 5th and 14th Amendments to the Constitution, and means that before the government can take away your liberty, it must first give the person the rights and process due to him or her under the Constitution. If the government has evidence that says you might be innocent, it would violate the fairness and impartiality of the trial process by just ignoring it and not letting the jury see it.

Durham County DA Mike Nifong lost his license and was jailed for withholding evidence
Mike Nifong Duke Lacrosse

This plays out in hundreds if not thousands of cases. In one high-profile case involving Duke University's lacrosse team, Mike Nifong, the Durham County prosecutor, withheld crucial DNA evidence from the defense team for six months. Eventually Nifong was removed as the prosecutor of the case, forced to resign as the county district attorney, lost his bar license, and spent time in jail. That may seem like a heavy penalty even though he eventually produced the material. But here's why it's not.

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