Usually, the test result and examiner’s opinion cannot be admitted in a California criminal proceeding unless all parties stipulate to admission of the results. The same rule generally bars references in court to an offer, refusal or taking of a polygraph. But statements made during an examination are not automatically excluded: they may be used if they are otherwise admissible under the rules that govern the particular statement. (Evidence Code § 351.1(a)–(b).)
That means a “pass” does not automatically prove innocence, and an excluded result does not make the interview harmless. Before agreeing to a test, release or recorded interview, have criminal counsel review the terms, setting and questions.
What may reach the courtroom?
| Item | General California rule |
|---|---|
| Test result or examiner’s opinion | Generally inadmissible unless all parties stipulate to admission of the results. |
| Reference to an offer, refusal or taking of the test | Generally inadmissible in the covered criminal proceedings, subject to the statute’s stipulation provision. |
| A statement made during the test or interview | Not excluded by § 351.1 just because it was made during an examination. It still must satisfy other evidence and constitutional rules. |
Evidence Code § 351.1 applies to criminal proceedings, including pretrial and postconviction hearings and juvenile offense proceedings. It is an evidence rule about what may be introduced in court; it does not prohibit investigators from requesting a test or determine what they may do outside court. (Evidence Code § 351.1)
The California Supreme Court has rejected attempts to use a defendant’s willingness to take a test, or a claimed favorable result, to bolster credibility without the required all-party stipulation. (People v. Espinoza; People v. Samuels)
Why the interview still matters
The statute preserves statements made during an examination when they are otherwise admissible. A court may therefore evaluate the recording separately from the result or examiner’s opinion. In People v. Westerfield, the Supreme Court discussed a taped posttest interview that was introduced after references to the polygraph were removed; the case also involved separate statements suppressed on Miranda grounds. The court’s treatment shows why the actual words, setting and recording matter. It does not mean every posttest statement is admissible. (People v. Westerfield)
If questioning occurs in custody, counsel should assess the full sequence: whether the person was in custody, what warnings were given, whether the person waived rights or asked for counsel, and whether any statement was voluntary. A polygraph request does not answer those questions by itself. People v. Gonzalez addressed custodial questioning by a polygraph examiner and a fact-specific dispute about a request for counsel. (People v. Gonzalez)
What does “all parties stipulate” mean?
The statute requires stipulation by all parties for results to be admitted. It does not say that the stipulation must be in writing. A written agreement may still define what is being offered and the consequences of an agreement. In People v. Trujillo, a written stipulation preceded admission of an adverse result; the case predates § 351.1 and is a caution to examine the agreement’s actual terms, not authority that current law requires a writing. Do not assume you can make results admissible alone, or that you can withdraw from an agreement after seeing a result.
Before deciding whether to take a test
Do not decide based only on the possibility that a result may stay out of court. Ask counsel to review:
- Who requested the examination and what investigative or court stage the case is in.
- Whether the test, questions, and any pretest or posttest interview will be recorded.
- The proposed release, waiver, stipulation or other written terms, if any.
- Whether questioning will occur in custody and the warnings, waiver or request-for-counsel history.
- Any interview or test already completed, including the complete recording and surrounding statements.
The separate question of speaking with a detective is covered in our California guide to voluntary detective interviews. For a specific polygraph request, the Law Offices of David S. Chesley can review the accusation and proposed interview or test terms before you decide. Call (800) 755-5174.