Reasonable doubt is the legal standard in criminal trials requiring the prosecution to prove a defendant’s guilt beyond a doubt that a reasonable person would find convincing. It’s not absolute certainty but a high threshold where any rational juror, after considering all evidence, would have no reasonable uncertainty about the defendant’s guilt. If such doubt exists—based on evidence, lack thereof, or inconsistencies—the defendant must be acquitted. It’s a cornerstone of the U.S. justice system, ensuring convictions require strong evidence, protecting against wrongful convictions. For example, if a jury finds conflicting witness testimonies or missing key evidence, that could create reasonable doubt.