Evidence law: what proof counts

The rules of proof control what a judge or jury may consider. For example, they decide whether a document, a recording or a witness’s statement can come in at trial. As a result, they shape the outcome of almost every contested case.

In federal court, the Federal Rules of Evidence apply. Most states have their own codes modeled on the federal rules, often with changes. Therefore, always check your own state’s code as well.

Our guides start with relevance, the threshold for all proof. Next come hearsay, authentication and the best evidence rule. Then come witnesses, experts, privileges and the burdens of proof.

Each guide quotes the rule or case it relies on and links to the official text. For help with a real case, talk to a licensed attorney in your state.

Each guide quotes the rule it explains. For instance, the hearsay guide quotes Rules 801 to 807, and the expert guide quotes Rule 702 as amended in 2023. You can also read the full federal court rules at any time. In addition, the glossary defines terms such as hearsay, authentication and privilege.

However, state courts apply their own codes. Their wording often tracks the federal rules, but the details can differ, so check the code that governs your court.