Polygraph examiner
Expert class library · Forensic science · Either side
A polygraph examiner who administers a lie detector examination, usually the comparison question technique, scores the physiological charts and testifies that the examinee was or was not truthful. Courts rarely let that opinion reach a jury: Alaska's highest court held after a full Daubert review that the technique has not been shown reliable, and Arizona keeps results per se inadmissible even under its Daubert-based rule. The main exception is a stipulated examination, which Ohio admits for credibility when both sides agreed in advance and the jury is told the limits.
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Questions this testimony turns on
- Was the examination stipulated in advance by both sides, and on what terms?
- Which technique was used, and what error rates do the studies the examiner relies on actually show?
- Was the examiner hired by the defense alone, without notice to the prosecution or a chance to observe?
- How does the examiner account for the base rate of truthful and deceptive examinees in turning a pass into a likelihood of truth?
- Did the examinee use, or refuse a second examination that could reveal, countermeasures?
Methods
- Comparison question technique
- Physiological chart scoring of respiration, skin conductance and cardiovascular responses
- Pretest interview and question formulation
- Countermeasure detection
- Error rate and base rate analysis
How the testimony is attacked
- Not shown reliable. The technique's accuracy has not been established by persuasive data. In State v. Sharpe the Alaska Supreme Court held, after reviewing the science under Daubert, that comparison question polygraph evidence is not sufficiently reliable to be admitted.
- No reliable base rate. A passed test says little without knowing how often truthful and deceptive people pass. The Sharpe court pointed to the lack of a reliable base rate as a core reason the results cannot show whether a defendant was likely truthful.
- Friendly examiner. An examination commissioned by one side, without notice to the other, may be biased toward the result that side wants, and courts weigh that risk.
- Per se inadmissibility. Many states bar polygraph results whatever the method. In Hansen v. Chon-Lopez the Arizona Court of Appeals held results remain per se inadmissible after Arizona adopted Daubert, and may not be put to a grand jury even as exculpatory evidence.
- Usurping the jury. Courts worry jurors will treat a lie detector result as conclusive on credibility, which is the jury's question to decide.
What the public record shows
Courts have filed at least 97 opinions since 2015 that discuss this class of testimony and cite Daubert or Rule 702, as of October 4, 2026. Three that show how courts handle this class of testimony:
| Outcome | Case | Court | Year | Why |
|---|---|---|---|---|
| Excluded | State v. Sharpe435 P.3d 887 | Alaska | 2019 | In three consolidated criminal cases where defendants offered a defense-hired examiner's opinion that they answered truthfully, the Alaska Supreme Court held comparison question polygraph evidence has not been shown sufficiently reliable under Daubert and Coon, citing disputed accuracy studies and the lack of a reliable base rate, and reversed the two orders admitting it while affirming the one excluding it. |
| Excluded | Hansen v. Chon-Lopez501 P.3d 762 | Ariz. Ct. App. | 2021 | The court held that polygraph results, which remain per se inadmissible at trial in Arizona even after it adopted the Daubert standard, may not be presented to a grand jury even when favorable to the defense and offered as clearly exculpatory evidence, though it granted relief on other grounds. |
| Admitted | State v. Reese2016-Ohio-557 | Ohio Ct. App. | 2016 | Affirming an aggravated murder conviction, the court held it was not plain error to admit the results of a polygraph the defendant failed after he and the State stipulated before testing that a failed result would be admissible, and that the standard jury instruction limiting the results to credibility satisfied the Ohio Supreme Court's conditions for stipulated polygraphs. |
Each case links to the free opinion text on CourtListener.
Many states treat polygraph results as inadmissible whatever the examiner's method, often as a fixed rule, and some admit them only when both sides agreed to the examination in advance. A full reliability hearing is the exception, not the rule.
In federal court: amended Rule 702
In federal court, since December 1, 2023, Rule 702 says expressly that the party offering an expert must show the court it is more likely than not that the testimony meets each requirement: that it rests on sufficient facts or data, uses reliable methods, and reflects a reliable application of those methods to the case. Questions about the basis of an opinion are no longer automatically matters of weight for the jury. For how the circuits have applied the amendment, see the Rule 702 tracker, which follows each court of appeals; for what that means for preparing or attacking this class of expert, see the guide on amended Rule 702.
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Updated October 4, 2026. How this page is built: rulings are found by searching court opinions on CourtListener. The summaries are written by AI working from the full text of each opinion, and every citation and link is checked automatically. Outcomes are labelled by what the court did with the expert’s testimony. No individual expert is named. This page summarises public decisions for orientation and is not legal advice; read the opinion before relying on any ruling. Spotted an error? Tell us.