KENOSHA, WISCONSIN (REUTERS) - A jury acquitted teenager Kyle Rittenhouse on Friday (Nov 19) of murder in the fatal shooting of two men in a trial that highlighted divisions over gun rights and stirred fierce debate about the boundaries of self defence in the United States.

The jury found Rittenhouse, 18, not guilty on all charges: two counts of homicide, one count of attempted homicide for wounding a third man, and two counts of recklessly endangering safety during racial justice protests marred by arson, rioting and looting on Aug 25, 2020 in Kenosha, Wisconsin.

Rittenhouse broke down sobbing after the verdict and collapsed to the floor before being helped back into his chair.

The verdict came shortly after the judge warned the courtroom to remain silent or be removed.

Amid a heavy law enforcement presence, several dozen protesters lined the steps outside the courthouse after the verdict was read, some carrying placards in support of Rittenhouse and others expressing disappointment.

"We are all so very happy that Kyle can live his life as a free and innocent man, but in this whole situation there are no winners, there are two people who lost their lives and that's not lost on us at all," David Hancock, a spokesperson for the Rittenhouse family, told Reuters.

Rittenhouse shot and killed Joseph Rosenbaum, 36, and Anthony Huber, 26, and fired a bullet that tore a chunk off the arm of Gaige Grosskreutz, 28. Rittenhouse claimed self defence.

The verdict was greeted with outrage by many on the political left and celebrated by gun rights supporters.

"It is unconscionable our justice system would allow an armed vigilante... to go free," the Congressional Black Caucus said in a statement.

US congressman Madison Cawthorn, a Republican representative from North Carolina, said on Instagram: "Kyle Rittenhouse is not guilty my friends. You have a right to defend yourselves. Be armed, be dangerous and be moral."

In reaching their verdicts after more than three days of deliberations, the jury contended with duelling narratives from the defence and prosecution that offered vastly different portrayals of the teenager's actions on the night of the shootings.

The defence argued that Rittenhouse had been repeatedly attacked and had shot the men in fear for his life. They said he was a civic-minded teenager who had been in Kenosha to protect private property after several nights of unrest in the city south of Milwaukee.

The unrest followed the police shooting of a Black man named Jacob Blake, who was left paralysed from the waist down.

The prosecution portrayed Rittenhouse as a reckless vigilante who provoked the violent encounters and showed no remorse for the men he shot with his AR-15-style rifle.

Live-streamed and dissected by cable TV pundits daily, the trial unfolded during a time of social and political polarisation in the US. Gun rights are cherished by many Americans and are enshrined in the US Constitution even as the nation experiences a high rate of gun violence and the easy availability of firearms.

Rittenhouse, who testified that he had no choice but to open fire to protect himself, is viewed as heroic by some conservatives who favour expansive gun rights and consider the shootings justified. Many on the left view Rittenhouse as a vigilante and an embodiment of an out-of-control American gun culture.

Protests against racism and police brutality turned violent in many US cities after the police killing of Black man George Floyd in Minneapolis three months before the Kenosha shootings.

The Rittenhouse verdict ended the highest-profile US civilian self-defense case since a man named George Zimmerman was acquitted in the fatal shooting of Trayvon Martin, an unarmed Black teenager, in Florida in 2013.

With so much of that night in Kenosha caught on cellphone and surveillance video, few basic facts were in dispute. The trial instead focused on whether Rittenhouse acted reasonably to prevent "imminent death or great bodily harm," the requirement for using deadly force under Wisconsin law.

The prosecution, led by Kenosha County Assistant District Attorney Thomas Binger, sought to paint Rittenhouse as the aggressor and noted he was the only one to kill anyone that night.

Full metal jacket

Rittenhouse's gun was loaded with 30 rounds of full metal jacket bullets, which are designed to penetrate their target.

The jury saw a series of graphic videos, including the moments after Rittenhouse fired four rounds into Rosenbaum, who lay motionless, bleeding and groaning. Other video showed Grosskreutz screaming, with blood gushing from his arm.

Rittenhouse testified in his own defence last Wednesday in the trial's most dramatic moment - a risky decision by his lawyers given his youth and the prospect of tough prosecution cross-examination. Rittenhouse broke down sobbing at one point but emphasised that he fired upon the men only after being attacked.

"I did what I had to do to stop the person who was attacking me," he said.

Rittenhouse testified that he shot Huber after he had struck him with a skateboard and pulled on his weapon. He said he fired on Grosskreutz after the man pointed the pistol he was carrying at the teenager - an assertion Grosskreutz acknowledged under questioning from the defence. Rittenhouse testified that he shot Rosenbaum after the man chased him and grabbed his gun.