What Is a Standard of Proof?
A standard of proof is the level of certainty a party must reach before a court will accept an allegation as fact (Clermont & Sherwin, 2002). The American legal system employs several standards, but the two most commonly encountered are the preponderance of the evidence, used in most civil proceedings, and beyond a reasonable doubt, required in criminal prosecutions (Cornell Law Institute, n.d.-a). A third intermediate standard, clear and convincing evidence, exists for certain matters such as fraud claims and civil commitment, but the preponderance and reasonable doubt standards represent the two poles of the spectrum most relevant to everyday legal proceedings (Cornell Law Institute, n.d.-b).
Beyond a Reasonable Doubt: The Criminal Standard
The beyond a reasonable doubt standard is the highest burden of proof in the American court system (Cornell Law Institute, n.d.-a). Its constitutional foundation was cemented by the United States Supreme Court in In re Winship (1970), in which Justice William J. Brennan, Jr. wrote that “the Due Process Clause protects the accused against conviction except upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged” (In re Winship, 1970, p. 364). The Court explained that the reasonable doubt standard “plays a vital role in the American scheme of criminal procedure” because it serves as “a prime instrument for reducing the risk of convictions resting on factual error” (In re Winship, 1970, p. 363).
The standard does not require the prosecution to eliminate all possible doubt, only all reasonable doubt. In Victor v. Nebraska (1994), the Supreme Court held that any jury instruction on reasonable doubt must convey to the jury that it must consider only the evidence and must properly state the government’s burden (Judicial Council of the Ninth Circuit, 2017b). The high threshold reflects the severity of the consequences a criminal defendant faces, including imprisonment and, in some jurisdictions, death (White Law PLLC, 2023).
Typical Criminal Jury Instruction
The Ninth Circuit Model Criminal Jury Instruction 3.5 provides a widely cited formulation:
Proof beyond a reasonable doubt is proof that leaves you firmly convinced the defendant is guilty. It is not required that the government prove guilt beyond all possible doubt. A reasonable doubt is a doubt based upon reason and common sense and is not based purely on speculation. It may arise from a careful and impartial consideration of all the evidence, or from lack of evidence. If after a careful and impartial consideration of all the evidence, you are not convinced beyond a reasonable doubt that the defendant is guilty, it is your duty to find the defendant not guilty (Judicial Council of the Ninth Circuit, 2017b, para. 1).
Similarly, the Michigan Committee on Model Criminal Jury Instructions instructs jurors that “proof beyond a reasonable doubt is proof that leaves you firmly convinced of the defendant’s guilt. A reasonable doubt is a fair, honest doubt growing out of the evidence or lack of evidence. It is not merely an imaginary or possible doubt, but a doubt based on reason and common sense” (Michigan Bar Journal, 2021, para. 3).
Preponderance of the Evidence: The Civil Standard
The preponderance of the evidence standard applies in most civil cases, including personal injury, contract disputes, and wrongful death actions (Cornell Law Institute, n.d.-b). Under this standard, the party bearing the burden of proof must demonstrate that its version of events is more probably true than not true (Judicial Council of the Ninth Circuit, 2017a). Courts and commentators often describe this threshold as “50 percent plus a feather” or “more likely than not” (LSU Law Center, n.d.).
The California Supreme Court defined preponderance of the evidence as simply requiring “the trier of fact ‘to believe that the existence of a fact is more probable than its nonexistence’” (In re Angelia P., 1981, as cited in Judicial Council of California, n.d., para. 2). The lower threshold reflects the nature of civil litigation, where the typical remedy is monetary compensation rather than the deprivation of liberty (White Law PLLC, 2023).
Typical Civil Jury Instruction
The Ninth Circuit Model Civil Jury Instruction 1.6 provides a representative example:
When a party has the burden of proving any claim [or affirmative defense] by a preponderance of the evidence, it means you must be persuaded by the evidence that the claim [or affirmative defense] is more probably true than not true. You should base your decision on all of the evidence, regardless of which party presented it (Judicial Council of the Ninth Circuit, 2017a, para. 1).
The California Civil Jury Instruction (CACI) No. 200 explains the concept in similarly accessible terms:
The parties must persuade you, by the evidence presented in court, that what they are required to prove is more likely to be true than not true. This is referred to as “the burden of proof.” … In civil trials, such as this one, the party who is required to prove something need prove only that it is more likely to be true than not true (Judicial Council of California, n.d., para. 2).
The O. J. Simpson Cases: A Study in Contrasting Standards
The Criminal Trial (1995)
On June 12, 1994, Nicole Brown Simpson and Ron Goldman were found stabbed to death outside Brown’s condominium in Los Angeles. O. J. Simpson was charged with both murders. The criminal trial, formally titled The People of the State of California v. Orenthal James Simpson, lasted eight months, from January 24 to October 3, 1995.
The prosecution presented forensic evidence, including DNA results linking Simpson to the crime scene. However, Simpson’s defense team challenged the credibility of the Los Angeles Police Department, alleging evidence contamination and racial bias in the handling of the case. The defense also highlighted that a leather glove recovered as evidence did not appear to fit Simpson’s hand, leading to attorney Johnnie Cochran’s now-famous refrain, “If it doesn’t fit, you must acquit” (Penn State University, 2020).
Applying the beyond a reasonable doubt standard, the jury deliberated for less than four hours before returning a verdict of not guilty on both murder charges in 1995. The defense had successfully raised enough doubt about the evidence to prevent the prosecution from meeting its constitutionally mandated burden. But years later, in a sad and stunning statement, juror Carrie Bess admitted that the not guilty verdict functioned as “payback” for the 1991 Rodney King beating, and said she believed roughly 90% of jurors felt that way (Edelman, 2016).
The Civil Trial (1996–1997)
Following the acquittal, the families of Nicole Brown Simpson and Ron Goldman filed civil suits against Simpson. Fred Goldman, Ron’s father, brought a wrongful death action, while the Brown family filed a survival suit for the assault and battery that resulted in Nicole’s death (Encyclopedia.com, n.d.).
Several key differences distinguished the civil trial. The burden of proof shifted from beyond a reasonable doubt to the lower preponderance of the evidence standard. Additionally, unlike in the criminal trial, Simpson could be compelled to testify, and the jury was permitted to draw adverse inferences from his responses (Encyclopedia.com, n.d.). The civil trial jury was also presented with additional evidence, including photographs of Simpson wearing the same style of Bruno Magli shoes that left prints at the crime scene, which Simpson had previously denied owning (Shortform, n.d.).
After five days of deliberation, in 1997, the jury unanimously found Simpson liable for the wrongful deaths of Ron Goldman and Nicole Brown Simpson. The jury awarded 8.5 million dollars in compensatory damages to the Goldman family and 12.5 million dollars in punitive damages to each family, totaling 33.5 million dollars (Encyclopedia.com, n.d.).
Why Two Different Outcomes?
The divergent outcomes are consistent with the law. In the criminal trial, the prosecution bore the burden of proving guilt beyond a reasonable doubt. The defense exploited weaknesses in the prosecution’s case, including concerns about evidence handling and the conduct of the Los Angeles Police Department, to create sufficient doubt in the jurors’ minds (Penn State University, 2020). However, the same body of evidence, when measured against the lower preponderance standard, was more than sufficient to establish that Simpson was more likely than not responsible for the deaths (Guerra LLP, 2025). The Simpson cases also illustrate that the two systems serve different purposes. The criminal justice system exists to determine whether the state may deprive a citizen of liberty; the civil system exists to compensate victims for harm. Because the stakes differ, so do the standards (Clermont & Sherwin, 2002).
Conclusion
The distinction between preponderance of the evidence and beyond a reasonable doubt is more than a legal technicality. It is a design feature of a system that calibrates the risk of error to the severity of the consequences. In criminal proceedings, society demands near-certainty before the state may imprison an individual. In civil proceedings, where the question is typically who should bear a financial loss, a simple probability assessment suffices. The O. J. Simpson cases remain the most prominent real-world illustration of how these two standards can produce starkly different outcomes from substantially the same set of facts.
