What was the officer’s defense?

The defense team said Mr. Stockley had plenty of reasons to know that Mr. Smith had a gun. Mr. Stockley testified that he had seen a gun in Mr. Smith’s hand inside the Buick after he initially approached Mr. Smith over a suspected drug deal in a parking lot, before the high-speed chase began. Mr. Stockley said that his partner also had yelled “Gun!” to signal that Mr. Smith had a weapon.

When the fatal confrontation occurred a short time later, after the high-speed chase, Mr. Stockley said, Mr. Smith was reaching for something as the officers stood at his driver’s side window, and he assumed it was a gun.

The defense rejected suggestions that the officer had planted anything. After the shooting, Mr. Stockley went back to the police vehicle to get a medical dressing that slows bleeding, they said, not to get an extra gun. An expert testified that someone can hold a gun and not leave DNA on it, so the absence of Mr. Smith’s DNA on the gun was not proof that he had not held it.

In the end, Judge Timothy Wilson of the St. Louis Circuit acquitted Mr. Stockley on Friday morning, saying he was “simply not firmly convinced of defendant’s guilt.”

What happened in St. Louis when the verdict was announced?

Protesters gathered within minutes of the verdict, and they have marched each day since then, in downtown streets, entertainment districts and a suburban mall. The marchers have included people of a wide range of ages and of different races, and their numbers and makeup have shifted significantly at various points during the weekend.

Most demonstrators have been peaceful, but there have been violent incidents after dark each night. At least 11 law enforcement officers have been injured, the mayor’s house was vandalized and windows were broken at several businesses and a public library.