In a Utah criminal jury trial, assessing credibility nearly always belongs to the jury—the people—composed from the people—by the people as the ultimate bulwark against injustice.
Jurors listen to the witnesses, consider inconsistencies, evaluate motives and demeanor, compare testimony with other evidence, and ultimately decide whom to believe.
But Utah law recognizes a very narrow and difficult exception to that general rule: the “inherently improbable” testimony doctrine.
In the past five years, Utah appellate decisions have addressed the inherently improbable doctrine in several cases.
The Utah Court of Appeals recently revisited the doctrine in State v. Hassan, 2026 UT App 132. The decision provides a useful reminder of both the existence of the doctrine and just how demanding the standard is. You should never place all your chances of trial success on the inherently improbable doctrine. It is that difficult.
What Is “Inherently Improbable” Testimony?
The doctrine originates principally from the Utah Supreme Court’s decision in State v. Robbins, 2009 UT 23, 210 P.3d 288.
Ordinarily, a court reviewing the sufficiency of the evidence accepts the jury’s credibility determinations. But Robbins recognizes an exception when testimony becomes so unreliable that it crosses the line from an ordinary credibility dispute into inherent improbability.
As the Court of Appeals explained in Hassan, testimony may qualify as inherently improbable when it is:
- Physically impossible, or
- Apparently false, sometimes described by Utah courts as “incredibly dubious.”
State v. Hassan, 2026 UT App 132, ¶ 39 (citing State v. Robbins, 2009 UT 23, ¶¶ 16, 18).
That is an exceptionally high standard.
The Three Hallmarks Utah Courts Examine
Utah appellate courts have identified three recurring hallmarks that can help determine whether testimony has become inherently improbable:
Material inconsistencies. The inconsistencies must matter. Minor discrepancies, imperfect recollections, differences in details, or ordinary contradictions generally remain questions for the jury. Minor inconsistencies are what juries are for. Disposing of conflicting evidence and testimony is the bread and butter of the American jury system.
Patent falsehoods. A statement that is demonstrably or physically impossible presents a substantially different issue from testimony that merely seems unlikely.
Lack of corroborating evidence. The absence of corroboration can contribute to an inherent-improbability analysis, particularly when combined with serious inconsistencies or apparent falsehoods.
Ordinary Inconsistencies Are Not Enough
This limitation is critical.
Witnesses contradict themselves. Memories change. People describe the same event differently. Cross-examination exposes discrepancies. Those problems are an ordinary part of trials—it is what the jury is for.
Utah courts therefore distinguish inherent improbability from ordinary credibility problems.
As Hassan reiterates, inconsistent testimony and conflicting accounts are commonplace at trial. The doctrine is not satisfied merely by raising what the Court of Appeals calls “garden-variety credibility questions.” Id. ¶ 42 (quoting State v. Corona, 2025 UT App 93, ¶ 28, 574 P.3d 988).
The inconsistencies must be substantial before testimony can properly be characterized as inherently improbable. Id. ¶ 43.
That distinction protects the constitutional role of the jury. A judge cannot simply decide that a witness seems unreliable and substitute the judge’s credibility determination for the jury’s.
Corroboration Does Not Have to Prove Everything
Another important feature of Utah’s doctrine concerns corroboration.
Corroborating evidence does not have to independently establish every part of a witness’s account. The Court of Appeals has explained that corroboration sufficient to defeat an inherent-improbability argument need only provide another source of evidence supporting some details of the witness’s story.
State v. Corona, 2025 UT App 93, ¶ 25.
Nor does Utah law require independent corroboration of the specific conduct constituting every charged offense. As Hassan reiterates, Utah’s inherent-improbability cases do not impose a requirement that there be corroborating evidence of each specific offense or each element. Hassan, 2026 UT App 132, ¶ 51 (citing State v. Jok, 2019 UT App 138, ¶ 25, 449 P.3d 610, aff’d, 2021 UT 35, 493 P.3d 665).
This makes a successful inherent-improbability challenge particularly difficult when independent evidence supports portions of the witness’s overall account.
The Difference Between “I Don’t Believe It” and “No Reasonable Jury Could Believe It”
Perhaps the easiest way to understand the doctrine is to distinguish two very different arguments.
The first is:
“This witness should not be believed.”
That is normally an argument for the jury.
The second is:
“This testimony is so inherently improbable that no reasonable jury could rely upon it to find guilt beyond a reasonable doubt.”
That potentially presents a legal sufficiency issue for the court.
The distinction is substantial. The inherently improbable doctrine does not permit courts to become a “thirteenth juror” whenever testimony appears questionable. It applies only in the unusual circumstance where the problems with the testimony are sufficiently profound that the ordinary deference afforded to a jury’s credibility determination can no longer resolve the problem.
A Utah jury’s assessment of a witness’s credibility is rarely overturned by the courts, whether at the appellate level or in the trial court.
Why the Doctrine Matters in Utah Criminal Cases
The doctrine can become particularly important in criminal prosecutions where the State’s case depends heavily upon testimony from a single witness.
Utah law does not generally require physical evidence, DNA, photographs, medical evidence, or multiple eyewitnesses before a jury can convict. The testimony of one young witness can itself constitute evidence. Even when it allegedly happened twenty years ago.
But there remains a constitutional requirement that the State prove every element of a criminal offense beyond a reasonable doubt.
A Useful Framework for Evaluating an Inherently Improbable Claim
When evaluating whether testimony might meet Utah’s inherently improbable standard, the relevant questions include:
- Are the inconsistencies actually material, or do they concern peripheral details?
- Does the testimony contain a statement that is physically impossible?
- Is there evidence demonstrating a patent falsehood?
- Is there independent evidence corroborating any meaningful portion of the witness’s account?
- Are the alleged problems merely competing versions of events that a jury is entitled to resolve?
- After considering the evidence as a whole, is the testimony so dubious that reasonable minds must have entertained a reasonable doubt?
The last question is ultimately the most important.
Inherently Improbable Does Not Mean Merely Improbable
For Utah criminal defense lawyers, the doctrine remains an important sufficiency-of-the-evidence type principle. But State v. Hassan reinforces the equally important point that the doctrine is a narrow exception to the jury’s traditional authority to decide witness credibility.
Utah Cases Discussing the Inherently Improbable Doctrine
- State v. Hassan, 2026 UT App 132.
- State v. Corona, 2025 UT App 93, 574 P.3d 988, cert. denied, 574 P.3d 525 (Utah 2025).
- State v. Barnes, 2023 UT App 148, 542 P.3d 108.
- State v. Jok, 2021 UT 35, 493 P.3d 665.
- State v. Robbins, 2009 UT 23, 210 P.3d 288.