Alexandria attorney James I. Burkhardt was acquitted by a federal jury yesterday of all charges related to an alleged plan to "buy protection" for a major Washington-area prostitution ring.

"Thank God for the jury system in this country," Burkhardt declared as he walked out of the courtroom, his arms around two reporters.

When the verdict was announced to a hushed courtroom shortly before 2 p.m., Burkhardt burst into tears and hugged chief defense lawyer Kenneth Michael Robinson.

The jury of eight women and four men deliberated for two hours, including time to eat lunch. Nearly all of the jurors smiled at Burkhardt as they left the courtroom after the verdict. "Thank you, thank you." Burkhardt said, tears streaming down his flushed cheeks.

One juror, Cynthia M. Elkin, said she reached a decision "real early" in the deliberations. "I personally didn't feel the need for any debate or discussion," said Elkin, an Arlington optician.

Elkin said the credibility of government witnesses was not a factor in her decision. The government simply did not prove its case she said.

"We heard a lot of facts that were not pertinent to the crime at all," she said, calling it the "juiciest" case she has sat on since she began jury duty a few months ago.

"The credibility of the witnesses was a factor," said another juror, a retired government worker who asked not to be identified. "If they could have had . . . some evidence of a payment, maybe things could have been different . . . The evidence presented wasn't all that convincing."

Burkhardt, 49, was charged with conspiracy and two counts of violating federal racketeering laws for allegedly helping to direct a lucrative prostitution ring headed by Louis Michael Parrish, who prosecutors said earned as much as $1 million a year from the business.

The government's case included the potentially explosive allegation that Parrish channeled $500 monthly cash payments through Burkhardt to former Alexandria prosecutor William L. Cowhig to avoid prosecution. That alleged scheme, the government contended, allowed Parrish's illegal sex business to flourish in Alexandria.

Burkhardt's indictment resulted from a two-year federal probe into allegations of possible corruption in Alexandria. Assistant U.S. attorneys Joseph Al Fisher III and Theodore S. Greenberg declined to say yesterday whether Burkhardt's acquittal would end the investigation.

Cowhig, who resigned last year after his acquittal at two state trials on unrelated bribery and gambling charges, has not been charged in the federal probe. Sources said he has been a target of the investigation.

Defense attorney Robinson maintained throughout the trial that the government indicted Burkhardt to force him to give evidence against Cowhig. "They don't give a damn about the truth. They want Bill Cowhig," Robinson said in his closing argument to the jury.

After the verdict, Robinson repeated his criticism of the government, saying that Burkhardt had been a victim of what he called the government's "conspiracy of zeal." Robinson, 36, a flamboyant former prosecutor, said Burkhardt's indictment "show's how a nice part of government can become an awfully destructive force."

"We did our constitutional duty," prosecutor Fisher said after yesterday's verdict. "We put on the evidence we had to let the system decide it."

"I thought it was a close case," he added. "It could have gone either way."

The charges against Burkhardt, a former president of the Alexandria Bar Association, grew out of his role as attorney, for a string of Parrish's out-call dating services and massage parlors, which went by such names as "Bunny's" and "Foxy Lady."

Burkhardt strongly denied making any payoffs during the four hours he spent on the witness stand in his own defense.He maintained that he provided only legal advice to the Parrish operation and took no role in directing the illegal sex business.

Judbe Oren R. Lewis instructed the jury that as a lawyer Burkhardt had the same responsibility to obey the law as any other citizen. "Don't treat him any differently than anybody else," Lewis told the jurors, "Don't penalize him and don't give him any benefit because he is a lawyer."

At the same time, Lewis told the panel not to judge Burkhardt adversely simply because he represented some of the prostitutes in the massage parlors, noting that under the U.S. legal system all criminals are entitled to lawyers.

Drawing an analogy to a lawyer representing a bank robber, Lewis noted that "because you represent a bank robber doesn't make you part of the bank robbery."

Lewis said the key question was whether Burkhardt overstepped his role as lawyer and advised Parrish's organization "on how to get around the law.You can't advise a client on how to commit a crime," Lewis said.

"I am not a police officer, I was a lawyer," Burkhardt said earlier on the witness stand. "I didn't feel that it was incumbent on me to raise red flags or go to police officers" with information about the Parrish operation.

The case turned on what Lewis called the "absolute contradiction" between the testimony of Burkhardt and that of his chief accusers, Parrish, 33, and two former Parrish lieutenants, Larry J. Wadino, 32, and Kathy Lynn Cladwell, 26.

The three began cooperating with the government after their convictions last year on federal charges related to the prostitution ring. The defense argued that the trio "concocted" their story in hopes of getting reduced prison sentences.

Robinson called Wadino and Caldwell dupes for Parrish, whom he decribed in court as a violent, dishonest drug user.

Parrish, during his testimony, called Burkhardt "an intimate adviser on almost everything I did." Parrish said under oath that he began making the alleged payoffs after meeting with Burkhardt and Cowhig at a Crystal City restuarant in late 1974 -- a gathering at which Parrish claims Cowhig promised not to prosecute his operation on charges of violating local massage parlor ordinances and state prostitution laws.

Burkhardt acknowledged that the meeting took place, but said its sole purpose was to see if Parrish was interested in buying an interest in a hotel Cowhig owned in the Bahamas.

Another former Parrish employe, Elizabeth Dane Pesaresi, testified that when she made plans to run her own prostitution business out of an Alexandria apartment, Cowhig assured her she was not in danger of being prosecuted. Pesaresi, who received immunity for her testimony, said Burkhardt introduced her to Cowhig.

The trial was marked by Burkhardt's testimony that he had extra-marital affairs with some Parrish employes. But he flatly denied the government's allegation that he received free sex in exchange for his legal advice.

Wadino, Parrish's former chief factotum, testified that he commited perjury at a 1975 rape trial after Burkhardt allegedly asked him to lie as a favor to then-prosecutor Cowhig. Burkhardt testified that he told Wadino "to tell the truth."

Judge Lewis, 77, whose outspoken style dominated the trial at times, told the jury that since Wadino admitted comitting perjury at the rape trial, his testimony in the Burkhardt case should be evaluated "with caution and . . . great care."