My understanding is that the burden of proof in a tort case is preponderance of evidence. that is, more likely than not. Consider the following:

Defendant hits the plaintiff. The plaintiff suffers a broken arm, and did not have one before he was hit. The act was witnessed by several people. I would guess that plaintiff would likely be able to prove his case by preponderance of evidence. Is that likely to be the case?

The plaintiff was also hit in the arm a few seconds later by a third party, X. This confuses the picture. A medical examination of the arm shows a broken bone by one blow, and internal bleeding by a lesser blow. So consider the following cases:

Case 1: The defendant is 6'0", 180 pounds, and X is 5'4", 120 pounds. (He may be even weaker, basically, "weak" to the point where he could not have administered the harder blow without an adrenaline rush.) I would guess the preponderance of evidence would work against the defendant. Is that the case?

Case 2, a: The defendant is the "weak man," and X is the stronger. I would guess that the preponderance of evidence would work in favor of the defendant. Is this true?

Case 2, b: The defendant is the weaker, but yelled at the plaintiff prior to hitting him, possibly creating the required adrenalin rush. Does this impact the result in 2a?

Case 3, Defendant and X are of equal size, leading to a 50-50 chance that each cast the harder blow that probably broke the arm. In addition, there is a non-zero chance that the softer blow may also have broken the arm, through leverage, etc. The defendant clearly cast one of the two blows. Does the preponderance of evidence work against him?

One more thing. Under (Arizona) State vs. McNair, Assault and battery is a crime, and even a "bystander" can become an accessory or accomplice that is equally guilty with the principal, if there was a relationship between them, or if they acted in concert (confronted the plaintiff together). Could defendant and X share criminal liability at least in Arizona? Does this extend to civil liability?

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    Both Defendant and X are guilty of assault and battery, since they both struck Plaintiff, presumably without justification. Whether they acted in concert or not won't change that, though it could be an aggravating factor and allow other charges. In the civil case it would probably be in Plaintiff's interest to have both Defendant and X as defendants, so no matter how the court apportions damages between the two, Plaintiff ends up with the same total award. Essentially who's more responsible for Plaintiff's injury becomes something Defendant and X need to fight over.
    – Ross Ridge
    Commented Feb 9, 2020 at 1:57
  • @RossRidge: Good comment. Why don't you turn it into an answer that I could upvote, and possibly accept.
    – Libra
    Commented Feb 9, 2020 at 1:59
  • Because it doesn't really answer your question, which seems to be about how an Arizona court would apportion damages between Defendant and X in various circumstances.
    – Ross Ridge
    Commented Feb 9, 2020 at 2:06
  • @RossRidge: I'll clarify my question for you. Under various scenarios, I made one party "bigger" than the other to raise a "preponderance of evidence" issue. Then I said, suppose Arizona "lumps" the two together under criminal liability. If this "lumping" extends to civil liability, does this erase the preponderance of evidence" issue?
    – Libra
    Commented Feb 9, 2020 at 2:11

1 Answer 1


You are starting with a very confused notion of proof and evidence

I'm going to ignore your examples because they simply confuse things.

The plaintiff makes an allegation; therefore the onus is on the plaintiff to prove the allegation

That means they must prove the facts that demonstrate that each of the elements of the alleged tort has taken place. For your example of battery; the elements are that the defendant (1) voluntarily took (2) positive action (3) with the intention of causing contact with the plaintiff (or another in the case of a "swing and a miss and a hit") that (4) directly causes contact.

It doesn't matter if that contact caused a broken arm or, indeed, any injury to the plaintiff - battery is actionable per se; it doesn't need to cause damage. On the facts you state, both the defendant and X committed battery.

In order to prove each of the elements, the plaintiff will provide evidence to the effect that each of the things that are required to have happened, happened. The defendant will introduce evidence showing that at least one of the things that are required to have happened, didn't happen. The trier of fact will give weight to the evidence (i.e. decide who, if anyone, they believe and who is selling a crock of s&%t) and decide whether the plaintiff has proved each element to the required standard: for preponderance of the evidence, this means they are satisfied it's more likely that the things that are required to have happened, happened rather than they didn't happen.

If they do that, they have proved their case.

However, the defendant may raise available defences. For example, necessity, self-defense, and consent are all defenses to battery. However, it is now the defendant alleging that these circumstances apply so the onus of proof is reversed.

Now you may think that who has the onus of proof when we are just looking at "more likely than not" doesn't really matter but you would be wrong. For example, if the evidence is questionable (e.g. the only witnesses are the parties themselves in a "he said/she said" situation where each clearly has an interest to distort the facts in their favor -intentionally or unintentionally) and one is not more credible than the other, remembering who has the onus suggests that the person who had it didn't meet it.

Only if liability has been established would the case move to the question of the quantum of damages.

  • Suppose there is corroborating evidence, third party witnesses, "pictures," or in the case of a "paper" tort, documents. Would that likely tilt the evidence one way or another?
    – Libra
    Commented Feb 10, 2020 at 2:06

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