Relevant Evidence in Criminal Trials

Not all evidence makes it before the jury in a trial. Rules of evidence exist to weed out unreliable evidence and promote fairness. The starting place for this analysis—determining what kinds of evidence can or can't be introduced—is relevance.

What Is Relevant Evidence?

Under the Federal Rules of Evidence, "[e]vidence is relevant if:

• it has any tendency to make a fact more or less probable than it would be without the evidence; and
• the fact is of consequence in determining the action."

Fed. R. Evid. 401.

Relevance is the basic building block of evidence rules. Only relevant evidence is admissible at trial. For evidence to be relevant, a logical connection must exist between it and the factual issue it offers to prove or disprove. The connection needn't be so strong that any single item of evidence alone proves or disproves the fact. It's good enough if the piece of evidence constitutes a link in a chain of proof along with other pieces of evidence. (As the famous legal authority McCormick put it long ago, "A brick is not a wall.") The main limitation of the relevance rule is that the connection must be based on reason and logic rather than bias and emotion.

Examples of Relevant Evidence in Criminal Cases

Evidence can take many forms, such as testimony, documents, recordings, or items. The judge will decide whether the evidence is relevant or not, but the opposing party must object to its introduction. Below are examples of criminal cases and evidence that's relevant and irrelevant.

Example: Ruby is charged with stealing costume makeup from a drugstore the night before Halloween.

• The prosecution wants to offer evidence that Ruby's mom had refused to buy her a Halloween costume. The evidence is relevant to prove that Ruby had a motive for stealing the makeup.
• The prosecution also wants to call the drugstore manager to testify that the makeup department suffers more thefts than any other department of the drugstore. This testimony would not be relevant because it does not relate specifically to Ruby.

Example: John is charged with sexual assault.

• His defense attorney wants to introduce John's credit card statements and receipts showing purchases in another state on the same day as the assault. The evidence is relevant, because John is trying to convince the jury he wasn't in the state when the assault happened.
• The prosecution wants to present evidence that John had sex with a woman at a party two weeks before the assault occurred. Unless there's a connection to the victim or assault at issue, this evidence is irrelevant.

Example: Lance is charged with drunk driving.

• The prosecution wants to introduce dashcam video showing Lance stumbling outside the squad car. This evidence is relevant to establish whether Lance was under the influence.
• The prosecution also wants to offer evidence that Lance is a member of a violent street gang. The evidence is irrelevant because the crime charged has nothing to do with gang activities. The evidence would only serve to stir up bias against Lance.

Example: Clare is charged with car theft.

• The prosecution wants to introduce evidence that Clare is part of gang that requires new members to prove their loyalty by stealing something from a rival gang. This evidence would be relevant to show Clare had motive to steal the car.
• Clare was arrested in her home, and the prosecution wants to offer evidence that the arresting officer found marijuana and an unregistered handgun there. Unless the prosecution can establish that the gun and drugs were somehow involved in the theft, there's nothing to connect them with the crime, making them irrelevant. The evidence would do almost nothing other than predispose the judge or jury against the defendant.

Is Relevant Evidence Always Admissible at Trial?

No. Evidence must be relevant to have any chance of admissibility, but not all relevant evidence is admissible at trial. Judges often exclude relevant evidence because of some other evidence rule. For example, otherwise relevant evidence may have a great potential to unfairly stir a judge's or jurors' emotions and prejudices. In such situations, the judge is supposed to balance the importance of the evidence against the risk of an unfair appeal to emotion. If the judge determines that the importance outweighs the risk of unfair prejudice, the judge admits the evidence. But, if the risk of unfair prejudice substantially outweighs the relevance, the judge excludes the evidence.

Judges have lots of discretion when it comes to making such rulings. As a general rule, a judge is much more likely to exclude evidence as prejudicial in a jury trial than when the judge is hearing the case without a jury.

Example: Adam is charged with assaulting Vicki with a knife; Adam claims self-defense. The prosecution seeks to offer the following as evidence: (1) the knife allegedly used in the assault, (2) a photograph of Vicki taken minutes after the fight, showing cuts on her face and arms, and (3) the blood-soaked T-shirt that Vicki was wearing at the time of the fight. A judge is likely to admit the knife and the photograph into evidence but might exclude the shirt as unduly prejudicial. The size and shape of the knife and the nature of Vicki's injuries are rationally related to the issue of whether Adam or Vicki was the aggressor in the fight. However, if the shirt doesn't provide much information about how the events unfolded, the judge will likely exclude it due to its potential to shock and disgust the jury.