4.1: STANDARDS OF PROOF

Probable cause

Many people assume that probable cause requires at least a 51% probability because anything less would not be “probable.” While this is technically true, the Supreme Court has ruled that, in the context of probable cause, the word “probable” has a some- what different meaning. Specifically, it has said that probable cause requires neither a preponderance of the evidence nor “any showing that such belief be correct or more likely true than false, “and that it requires only a “fair” probability, not a statistical probability. Thus, it is apparent that probable cause requires something less than a 50% chance. How much less? Although no court has tried to figure it out, we suspect it is not much lower than 50% (Alvarez, 2020).

Reasonable suspicion

As noted by Alvarez (2020), the required probability percentage for reasonable suspicion is a mystery. Although the Supreme Court has said that it requires “considerably less [proof] than preponderance of the evidence” (which means “considerably less” than a 50.1% chance), this is unhelpful because a meager 1% chance is “considerably less” than 51.1% but no one seriously thinks that would be enough. Equally unhelpful is the Supreme Court’s observation that, while probable cause requires a “fair probability,” reasonable suspicion requires only a “moderate” probability. What is the difference between a “moderate” and “fair” probability? Again, nobody knows. What we do know is that the facts need not rise to the level that they “rule out the possibility of innocent conduct.” As the Court of Appeal explained, “The possibility of an innocent explanation does not deprive the officer of the capacity to entertain a reason- able suspicion of criminal conduct. Indeed, the principal function of his investigation is to resolve that very ambiguity.” We also know that reasonable suspicion may exist if the circumstances were merely indicative of criminal activity. In fact, the California Supreme Court has said that if the circumstances are consistent with criminal activity, they “demand” an investigation.”

Beyond a Reasonable Doubt

Evidence that is beyond a reasonable doubt is the standard of evidence required to validate a criminal conviction in most adversarial legal systems. ^[1] Generally, the prosecutor has the burden of proof and is required to prove their case to this standard.^[2] This means that the version of events being presented by the prosecution must be proven to the extent that there could be no "reasonable doubt" in the mind of a "reasonable person" that the defendant is guilty.^[3] There can still be a doubt, but only to the extent that it would not affect a reasonable person's belief regarding whether or not the defendant is guilty. Beyond "the shadow of a doubt" is sometimes used interchangeably with beyond reasonable doubt. But this term extends beyond the latter, to the extent that it may be considered an impossible standard. The term "reasonable doubt" is most commonly used.

If doubt does affect a "reasonable person's" belief that the defendant is guilty, then the jury is not satisfied beyond "reasonable doubt". The precise meaning of words such as "reasonable" and "doubt" are usually defined within jurisprudence of the applicable country. A related idea is William Blackstone's formulation: "It is better that ten guilty persons escape than that one innocent suffer"^[4] (Legal Burden of Proof, 2020).

Preponderance of Evidence

Burdens of proof vary, depending on the type of case being tried. The plaintiff’s burden of proof in a civil case is called preponderance of evidence. Preponderance of evidence requires the plaintiff to introduce slightly more or slightly better evidence than the defense. This can be as low as 51 percent plaintiff to 49 percent defendant. When preponderance of evidence is the burden of proof, the judge or jury must be convinced that it is “more likely than not” that the defendant is liable for the plaintiff’s injuries. Preponderance of evidence is a fairly low standard, but the plaintiff must still produce more and better evidence than the defense. If the plaintiff offers evidence of questionable quality, the judge or jury can find that the burden of proof is not met and the plaintiff loses the case (Legal Burden of Proof, 2020).