Burden of Proof: Definition & Cases

Instructor: Brittany McKenna

Brittany is a licensed attorney who specializes in criminal law, legal writing, and appellate practice and procedure.

Burden of proof refers to a party's duty in a criminal or civil trial to prove that a claim is true. This lesson introduces the general concept of a burden of proof, and discusses the related legal standards and Supreme Court cases.


I'm sure you never actually would, but imagine that you've been arrested for armed robbery. You hire an attorney to represent you. You're eager to get in front of a jury and explain yourself, but your attorney tells you that you aren't under any obligation to prove your innocence. You're familiar with the phrase 'innocent until proven guilty,' but you've never thought about what the phrase really means!

Let's discuss this concept further...

Burden of proof refers to the duty of a party making a claim to prove that the claim is true. The phrase is most commonly used in the context of criminal trials, where the defendant (the party charged with a crime) is presumed innocent until proven guilty. In a criminal trial, the obligation to prove the defendant's guilt belongs to the government. In a civil trial, it's the plaintiff (the party making a claim for civil damages) who carries the burden of proof. Because the burden of proof belongs to the party making the claim, the party against whom the claim is made is under no obligation to prove their innocence, or to prove that their position is the correct one.

It's important to remember that burden of proof doesn't only refer to the amount of evidence presented. Rather, the quality of the evidence produced is as important as the amount of evidence presented.

Legal Standards of Proof & Cases

In the United States justice system, the legal standard of proof defines what's required of the prosecution to satisfy the burden of proof in a case. Think of these standards as rungs on a ladder. As you climb up the ladder, the standard of proof becomes harder to meet.

Reasonable Suspicion

The lowest standard of proof is reasonable suspicion. Reasonable suspicion applies to a specific set of circumstances related to police searches. When a police officer wants to conduct a brief stop and search of a suspect, the officer must have reasonable suspicion that a crime is being committed.

The reasonable suspicion standard was established in the United States Supreme Court's Terry v. Ohio decision. In Terry v. Ohio, the Supreme Court decided that a police officer may stop a person in order to quickly search the outer layers of their clothing for weapons, but only if the officer has a reasonable suspicion that the person just committed a crime or is about to commit a crime. The Supreme Court defined a reasonable suspicion as a 'specific, articulable, and individualized' suspicion. That is, a suspicion that's specific to the circumstances that can be easily explained by the officer. Reasonable suspicion requires more than hunch that a crime is being committed.

Reasonable to Believe

The next stop on the standard of proof ladder is the 'reasonable to believe' standard. The reasonable to believe standard is applied to determine when an officer may search a suspect's vehicle after arrest. Under this standard, an officer may search an suspect's vehicle after his arrest only if it's reasonable to believe that more evidence will be found in the vehicle.

The 'reasonable to believe' standard of proof was first established by the Supreme Court in Arizona v. Gant. Rodney Gant was arrested for driving on a suspended license. Officers stopped and detained Gant and his passengers after they parked and exited Gant's car. The officers then searched the car and found weapons and drugs. The Supreme Court ruled that the officers were permitted to search Gant's car under those circumstances because there it was reasonable to believe that more evidence would be found in the car.

Probable Cause

The probable cause standard of proof is most commonly applied to arrests and searches. In the context of a search for drugs or weapons, an officer must believe that there's a 'fair probability' that evidence of crime will be found during the search in order to satisfy the probable cause standard. An officer must believe there is a fair probability that a crime has been committed in order to have probable cause to arrest the suspect.

Imagine you're an agent from the Drug Enforcement Agency (DEA). You're on patrol at an international airport when you're notified by airline employees that a traveler is acting suspicious. The traveler, 'Tony Trafficker' we'll call him, paid for his tickets in cash, is traveling under a fake name, didn't check any bags, and acted nervous during his flight. You suspect that he's a drug trafficker. Do you have probable cause to arrest Tony? Because you believe that there's a fair probability that Tony is a drug trafficker, the probable cause standard is satisfied. The Supreme Court encountered this set of facts in United States v. Sokolow.

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