Kyle Rittenhouse will argue self-defense. Experts say proving the argument to a jury isn't easy.

MILWAUKEE — Within hours of the shootings in Kenosha, Wisconsin, last year, supporters were clamoring that Kyle Rittenhouse acted in self-defense, and his lawyers said it was so obviously lawful self-defense that charging him was nothing but a political move.

But is it that clear cut? The prosecution thinks it's so clearly not self-defense that it charged one of the three shootings as first-degree intentional homicide. 

In Wisconsin, self-defense works like this: If a jury is convinced Rittenhouse reasonably feared he would be killed or seriously hurt by Joseph Rosenbaum, Anthony Huber and Gaige Grosskreutz, he would be found not guilty of most of the shootings.

Rittenhouse need only make "some showing" of self-defense before the burden shifts to prosecutors to prove, beyond a reasonable doubt, Rittenhouse's belief only deadly force would save him was either dishonest or unreasonable.

Before deliberating, the jury would hear instructions about how the privilege of self-defense applies.

"The keys are whether the defendant actually believed (shooting the men) was necessary to save himself from imminent death or great bodily harm," said Michael O'Hear, professor of criminal law at Marquette Law School.

"And second, and probably the real battle at trial, was it reasonable to believe that?" O'Hear said. "It's a very open-ended determination and the jury is invited to use its own values, experience and common sense."

So-called perfect self-defense results in complete acquittal.

In the death of Huber, Rittenhouse is charged with first-degree intentional homicide, which raises the potential of imperfect self-defense, when a defendant proves an honest — but unreasonable — belief he had to resort to deadly force.

In such instances, the defense can mitigate the charge to second-degree intentional homicide, which does not carry the same mandatory sentence of life in prison.

What the law says about retreat in Wisconsin and how it will play out in the Rittenhouse trial

While Wisconsin law does not contain a specific duty to retreat from attack, the presence or absence of opportunity to retreat can factor into the analysis of whether deadly force was reasonable under the circumstances. 

"The jury instruction kind of speaks out of both sides of its mouth on retreat," O'Hear said. "On the one hand, there's no duty, but the jury could find you don't qualify for self-defense because you didn't retreat. The law is a little messy on retreat in Wisconsin."

Rittenhouse's first victim, Joseph Rosenbaum, was unarmed when he began running at Rittenhouse, who chose to run in between some parked cars.

Rittenhouse's lawyers have advanced the theory Rosenbaum, who, because he was a felon and could not legally possess a gun, was trying to take Rittenhouse's rifle from him, and could have then killed Rittenhouse.

The general scenario plays out frequently in police shootings where officers say they feared a person was reaching for their or another officer's weapon. The argument is that by carrying a gun you're then entitled to use it against someone you think might take it and shoot you.

O'Hear said that approach often makes him uncomfortable in police shooting cases.

"They're almost always armed on duty," he said. "If you really push that argument, it's like carte blanche to use their weapons."

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Rittenhouse had already fallen to the street when an unknown man ran up on him and unleashed a flying jump kick. Rittenhouse fired two shots that missed. For that, he's charged with first-degree recklessly endangering safety.

Prosecutors could argue Rittenhouse had the entire open area to retreat, but the defense would say he was surrounded by an angry crowd and could not escape the threats of violence.

Huber then hit Rittenhouse with a skateboard, and tried to take his rifle. Rittenhouse killed him with a single shot to the stomach. A defense expert said the skateboard could be considered a deadly weapon.

His family and other witnesses say Huber, believing Rittenhouse had already killed someone, was trying to disarm him. Rittenhouse is charged with first-degree intentional homicide in Huber's death.

Just as Rittenhouse shot Huber, Grosskreutz was walking up to Rittenhouse. He briefly stopped and raised his hands after Huber was shot, holding a handgun in his right hand. Rittenhouse, still seated on the pavement, looked up and shot Grosskreutz in the right bicep. Prosecutors charged attempted first-degree intentional homicide.

A defense expert testified at a pretrial hearing that Rittenhouse fired all four shots at Rosenbaum in less than a second, and that seven seconds elapsed between his shot at the attempted kicker, and when he shot Grosskreutz. The expert is expected to testify about that, and human reactions to sudden stimuli, but will not be allowed to offer an opinion or whether or not Rittenhouse's reactions were reasonable — the ultimate question the jury must decide.

Experts on the use of force typically appear on behalf of police officers accused of using excessive force of one kind or another. O'Hear sees some comparison with such cases, but with the difference that Rittenhouse, who lacks professional training about how and when to legally use a gun for protection, might have an easier time proving that, to him, it was a reasonable response.

"On the other hand," O'Hear said, "the fact that he's not a law enforcement officer, but trying in some ways to act like one — protecting property, order and safety, as an untrained but armed civilian, doesn't necessarily put him in a sympathetic light."

Provocation is 'complicated part of the law' that could play into self-defense

There's yet another potential wrinkle to Rittenhouse invoking the privilege of self-defense. As the Wisconsin jury instruction reads: "A person who engages in unlawful conduct of a type likely to provoke others to attack, and who does provoke an attack, is not allowed to use or threaten force in self-defense against that attack."

Except if the provocateur thinks he's in imminent danger of death or great bodily harm — and then slightly different rules apply.

O'Hear called provocation "an interesting and complicated part of the law," of self-defense. 

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Though his lawyers dispute it, for now, it was unlawful for Rittenhouse, at 17, to be carrying around an assault-style rifle. Could that alone, given the context, provoked Rosenbaum to chase him? 

Once he shot Rosenbaum, which appeared to observers at the time to be a crime, did that provoke Huber and Grosskreutz to attack Rittenhouse, either in anger or to try to stop further violence?

"I think there's something to that," O'Hear said, "and I've been wondering if the state might raise that." 

But he said while Rittenhouse's behavior was likely inappropriate, or threatening to some, it might be difficult to argue that it would provoke an attack against him, given he was armed with a rifle.

If Rittenhouse's actions are seen as a provocation, he can still assert lawful use of deadly force if he reasonably believed his own death or great harm was imminent, and he believed he had "exhausted every other reasonable means to escape from or otherwise avoid" those possible consequences.

Follow Bruce Vielmetti on Twitter at @ProofHearsay.