Evidence rules (US and UK)

Authenticating text messages under Federal Rule of Evidence 901

Last reviewed 2026-10-17 · 2 official sources cited below

Before a judge or jury considers a text message, the person offering it generally has to authenticate it: show it is what they say it is. Here is what the U.S. federal rule says, in plain terms. Most states have similar rules, and judges apply them case by case.

The rule

FRE 901(a): “To satisfy the requirement of authenticating or identifying an item of evidence, the proponent must produce evidence sufficient to support a finding that the item is what the proponent claims it is.”

It’s a threshold. The judge decides whether there is enough evidence that a reasonable person could find the item genuine. The other side can still argue it isn’t.

Examples the rule lists that often come up with messages

FRE 901(b) gives examples, “not a complete list”. Several are commonly relevant to texts:

• (b)(1) Testimony of a witness with knowledge: for example, a participant testifying that this is the conversation they had with that person.
• (b)(4) Distinctive characteristics and the like: “the appearance, contents, substance, internal patterns, or other distinctive characteristics of the item, taken together with all the circumstances”, such as nicknames, references to events only the sender would know, or replies that make sense in sequence.
• (b)(9) Evidence about a process or system: evidence describing a process or system and showing that it produces an accurate result.

Self-authentication for certified electronic copies

FRE 902(14) allows data copied from an electronic device, storage medium or file to be self-authenticating if it is authenticated “by a process of digital identification”, shown by a certification of a qualified person, with notice to the other side. The committee notes explain that this is “ordinarily” done with hash values. This route needs a qualified person’s certification. A PDF tool alone doesn’t satisfy it. See SHA-256 hashes as evidence.

Practical steps people take

• Keep the phone and the original conversation; don’t delete or edit it.
• Export the chat with the app’s own feature and keep the export file unchanged.
• Note when, how and from which device you exported, and with what software.
• Use a complete, chronological transcript so context is visible.
• Record the export file’s hash so anyone can verify the transcript came from that file.

None of this guarantees admissibility. If authenticity is likely to be contested, for example the other side says “I never sent that”, talk to a lawyer. Forensic extraction by an expert may be appropriate.

Sources

1. Federal Rules of Evidence, Rule 901 — Authenticating or Identifying Evidence (Cornell LII)
2. Federal Rules of Evidence, Rule 902 — Evidence That Is Self-Authenticating, incl. 902(13)–(14) and committee notes (Cornell LII)

Sources were opened and checked on 2026-10-17. Laws and rules change; always read the current version.