A federal jury in San Antonio yesterday acquitted white former Florida police officer Charles Veverka on all four charges that he violated the civil rights of a black man who was beaten to death in an incident that led to riots in Miami last spring.

After a week-long trial and 16 hours of deliberation, the jurors -- six whites, five Mexican Americans and one black -- broke an 11-to-1 deadlock that had threatened a mistrial.

In Miami, police ringed predominantly black central city neighborhoods with "precautionary" barricades last night after reports of isolated rock-throwing incidents.But no serious racial violence was reported. Dade County authorities said police officers had a "tactical operations plan" ready should trouble occur.

The state of Florida had granted Veverka, 30, immunity in exchange for his testimony in the criminal trial in May of four other Dade County police officers. Riots exploded in Miami's predominantly black Liberty City area after the officers were acquitted by an all-white jury in that trial in Tampa. They were charged with beating black insurance executive Arthur McDuffie to death with their flashlights and then trying to make it look like an accident.

In the aftermath of the riots, a federal grand jury indicted Veverka on civil rights charges. His trial was moved to San Antonio because of fears it would trigger more racial animosity if it were held in cities closer to Miami.

As yesterday's verdict was read, Veverka's head sagged, and his chief defense attorney, Denis Dean, put his arm around the defendant.

"When I heard the jury was deadlocked 11 to 1, I honestly thought it was 11 for guilty and one not guilty. I'm happy, naturally. . . . It is the best Christmas prsent I could have," Veverka said.

Veverka, who now works in Miami as a security guard, said he intended to cooperate in any ongoing investigation of the cover-up of McDuffie's death. Federal prosecutor Brian McDonald said the investigation would continue, while Atlee Wampler III, a U.S. attorney in Miami, said the verdict would probably affect investigations against other former officers. tNo other federal indictments have been handed down in the case, a Justice Department spokesman said.

A factor in Veverka's acquittal yesterday, said jury foreman Pat McNamara, was the fact that the former policeman had volunteered statements about the McDuffie beating.

"One factor . . . was the defendant's confession, because it was made without an attorney in what appeared to be a truthful a manner as he could muster," McNamara told reporters. "It was overwhelmingly proved that the underlying crime had been committed. There was no doubt Arthur McDuffie had been beaten to death by police. Every single juror wanted to react to that crime, but we couldn't in good conscience bring in a guilty verdict" on Veverka.

Garth Reeves, editor of the Miami Times, a Florida black newspaper, said he felt most blacks would not be surprised by the verdict.

"I don't think the criminal justice system has been bettered. It's the same around the country -- Tampa, Atlanta, San Antonio," he said. "I think it's a reluctance on the part of white America to punish a white police officer for a crime against a black man."

Federal prosecutors charged Veverka with being an accessory to the beating and with falsifying police reports afterward. The prosecution's evidence included a sworn statement by Veverka that he had falsified the reports on orders of his supervisor, according to wire service reports, to make McDuffie's injuries look like the result of a motorcycle accident.

The jury broke its deadlock after reporting on Tuesday to U.S. District Court Judge William Hoeveler that they were "hopelessly" deadlocked. Hoeveler, the Florida judge who moved the proceedings to Texas, yesterday sent them back with a plea to "try again."

The incident that started it all occurred last Dec. 17, exactly a year before yesterday's verdict. McDuffie's skull had been shattered like an egg, according to the medical examiner in the case.

McDuffie was killed after allegedly running a red light on his motorcycle and leading the Dade County (Metro) police on a high speed chase.

"I got splattered with the blood," Veverka had testified in the earlier trial of his fellow officers, as he described the macabre scene.

He said he was one of the first policemen to reach McDuffie after the chase and that he pulled the black man from his motorcycle, hit him once and then tried to pull him away from the growing crowd of other officers. When one officer started landing blows on McDuffie, Veverka said, "I turned my back and walked to the car."

The Miami riots, which resulted in 18 deaths, hundreds of injuries and more than $100 million in damage, focused the nation's attention on smoldering racial bitterness in the melting-pot city, caused in part by a feeling among blacks and other minorities that white justice translates into justice for them.

As word of the verdict came out last night, leaders in Miami's black community called for calm.

McDuffie's mother, Eula, declined to make a statement on the Veverka verdict, but, her attorney, Carol King Guralnick, said, "She said she wanted people to know that she didn't want any rioting, looting or personal injury because that is not going to help the black cause. . . ."

Guralnick said she and Mrs. McDuffie were in San Antonio last week for the trial and "we were treated very badly by everyone from the cab driver to the people at the hotel. We got the feeling after we had been there that it [the verdict] was going to turn out this way."