In a criminal trial, the prosecution will introduce evidence of the charged crime, and the defendant will usually (though not always) challenge the evidence, by questioning its reliability or relevance. Sometimes, the defendant will mount an alibi defense, or assert insanity or any number of other “affirmative defenses,” and ask the jury to believe these, instead. At the end of the trial, the judge or jury will decide whether the prosecutor has proved its case “beyond a reasonable doubt,” or whether, instead, the defense has proved its version of events.
The state’s obligation to prove its case begins with producing evidence on every element of the charged crime; unless it meets this “burden of production,” the defendant will be entitled to an acquittal. For example, imagine a theft case, which will require the state to prove (among other things) that the defendant took property belonging to another. If the prosecutor never introduces evidence as to who owned the subject of the theft, the judge will acquit the defendant.
Most prosecutors are careful to make sure they have evidence of every aspect, or element, of the charged offense. Their next job is to convince the judge or jury that the evidence is sufficiently believable; that they’ve proved every element “beyond a reasonable doubt.” This standard of proof is in the U.S. Constitution, and it will be explained to a jury every time they are directed to deliberate. An example of this explanation comes from a jury instruction widely used in California: “[Reasonable doubt] is not a mere possible doubt; because everything relating to human affairs is open to some possible or imaginary doubt. It is that state of the case which, after the entire comparison and consideration of all the evidence, leaves the minds of the jurors in that condition that they cannot say they feel an abiding conviction of the truth of the charge.” (California Jury Instructions—Criminal, CA CALJIC 2.90.)
Sometimes, defendants will concede that the prosecution has proved every element of the charged crime, but will offer reasons why they should not be convicted. These reasons are called “affirmative defenses,” and they include claims of self-defense, necessity, insanity, and so on. For example, a murder charge requires the prosecutor to prove three things: that the defendant 1. killed, 2. another person, 3. with the intent to do so. Defendants may concede all three issues, but argue that the killing was justified as an act of self-defense.
When self-defense is at issue, it’s up to the defendant to produce evidence, obviously. But what happens next? Here’s where things get tricky.
The states’ approaches to affirmative defenses can get pretty complicated. For more information on affirmative defenses, see our article, “Affirmative Defenses in Criminal Cases.”