Retired Navy communications expert Jerry Alfred Whitworth -- the last of four Navy men charged in the Walker spy ring to face trial -- was convicted today of passing highly sensitive Navy coding secrets to the Soviet Union in an espionage conspiracy that prosecutors described as the most damaging since World War II.

A jury of seven women and five men deliberated for 52 hours over 10 days before finding Whitworth, 46, guilty of 12 of 13 counts of espionage and federal income tax violations.

The jurors could not agree on the remaining charge, that Whitworth unlawfully obtained a manual detailing communications plans in the event of hostilities in the Mideast. The manual was found during a search of Whitworth's Davis, Calif., mobile home.

The protracted deliberations sparked speculation that the jury may have accepted the defense argument that Whitworth thought the material was going to Israel, an ally of the United States, and therefore did not intend to harm his country. U.S. District Judge John P. Vukasin Jr. instructed jurors that to convict Whitworth of espionage, they had to find not only that he passed classified documents but that he did so with the intent of injuring the United States or helping the Soviets, as the government charged. In finding Whitworth guilty of seven of eight counts of espionage, the jurors indicated that they sided with the government on that point.

Whitworth, who is to be sentenced Aug. 28, faces maximum penalties of seven life terms plus 17 years in prison.

U.S. Attorney Joseph P. Russoniello said, "It's hard to express how vigorously we will press the court to impose the maximum sentence available."

In a news conference after the verdict, Russoniello said Whitworth was, "in terms of damage to the United States and in terms of relative culpability . . . by far the more significant player" than John Anthony Walker Jr., the admitted mastermind of the espionage ring and the chief witness against his former Navy colleague.

But defense lawyer James Larson said, "Whatever Jerry Whitworth may have done, this trial should have been John Anthony Walker's."

Walker "is the acknowledged master spy of this espionage ring" who "got his last 20 pieces of silver for betraying Jerry Whitworth in this trial," Larson said, while "Jerry is just another one of Walker's victims."

Walker pleaded guilty to espionage charges last October and agreed to testify against Whitworth in exchange for more lenient treatment for his son, Navy Seaman Michael Lance Walker, who also pleaded guilty to espionage.

Noting that testimony at the trial, which began March 24, had covered "virtually every aspect of the defendant's life," Vukasin said he was "prepared to impose sentence at this time."

But Larson asked him to postpone sentencing in order to give the defense time "to inquire into certain possibilities."

Larson said later that the idea of Whitworth telling the government what information he had compromised "would certainly be one possibility to explore."

Russoniello, however, said, "There is nothing that Jerry Whitworth can do at this point as far as the government is concerned to lessen" the sentence that prosecutors will seek. "He has no information that we don't already have."

Whitworth, who was wearing a blue suit, chatted calmly with his lawyers before the jurors returned. He showed no emotion, casting his eyes downward, as the court clerk read the guilty verdicts.

Whitworth's wife, Brenda Reis, who had attended the highlights of the three-month trial, was not present for the verdict.

The chief prosecutor, Assistant U.S. Attorney William S. Farmer hit his fist on the table in glee as he heard the first guilty verdict.

Whitworth was convicted of passing Walker copies of highly sensitive Navy codes and design manuals for coding machines.

In closing arguments, Assistant U.S. Attorney Leida B. Schoggen described the information as "the most precious of our military secrets."

Whitworth, who was unemployed at the time of his arrest in June 1985 and has been held without bond since, also was found guilty of filing false income tax returns and conspiring to commit tax fraud with Walker by hiding the proceeds of the spy operation.

Whitworth received $332,000 for his role in the conspiracy, which lasted from 1974 until 1985.

In the course of the lengthy trial, prosecutors presented about 135 witnesses and introduced thousands of exhibits.

In closing arguments, Farmer called the spy ring "the biggest hemorrhage in the history of this country's military secrets."

The defense was brief, with just 15 witnesses testifying over four days.

Defense lawyers sought to discredit Walker and portray Whitworth as a loyal friend and staunch anticommunist who would never have spied for the Soviet Union.

Whitworth, a senior chief radioman who retired from the Navy in 1983 after a 21-year-career, did not take the stand.

In his closing argument, defense lawyer Larson conceded that "there's absolutely no question" Whitworth "received money, and a lot of it," for supplying classified material to Walker, and that -- late in the espionage partnership -- Whitworth realized Walker's "buyer" was the Soviet Union.

He also admitted that Whitworth was the author of a series of anonymous letters to the FBI in 1984 confessing participation in a Soviet espionage ring.

Larson argued, however, that Whitworth acted under the "benevolent and mistaken belief that the classified information he passed would be going to an ally," namely Israel.

Consequently, he said, Whitworth did not have the required intent or reason to believe that his actions would aid the Soviet Union or harm the United States.

Farmer dismissed the defense argument as a "Fantasy Island version of what really happened."

The star prosecution witness was the man Larson described as "the Godfather of the First Family of espionage," John Walker.

Testifying in matter-of-fact, business-like terms, the Norfolk private detective and former Navy chief warrant officer provided the first public description of the spy ring he masterminded for nearly 18 years.

Following him on the witness stand was a parade of Walker family members, including the ex-wife who turned him in, Barbara Joy Crowley Walker; the daughter he tried to recruit as a spy, Laura Mae Walker Snyder, and the son and brother who joined him in the "spying business." Arthur Walker, John Walker's brother, was convicted of espionage in August.

The conviction of Whitworth caps a remarkable spate of espionage prosecutions that opened with the arrest of John Walker on May 20, 1985, the day after he dropped a bag of classified documents, carefully disguised as trash, for his Soviet contact on a lonely road in Poolesville in western Montgomery County.

In the following months of what came to be known as the year of the spy, the FBI charged 11 other individuals with spying for Ghana, Israel, China and the Soviet Union. Whitworth was the last to stand trial, although former CIA agent Edward L. Howard remains a fugitive from charges that he was a spy for the Soviets.

The Walker case in particular captured public attention, prompting congressional moves to reinstate the death penalty for espionage and military-wide measures to tighten security and limit dissemination of classified information.

Walker testified that he started spying in 1968, making contact with the Soviets by strolling into the Soviet Embassy in Northwest Washington.

Whitworth and Walker met two years later, when Walker was the director, and Whitworth an instructor, at a Naval radioman training school in San Diego.

The two men became good friends, spending weekends sailing on Walker's boat, "The Dirty Old Man." Walker began to consider bringing Whitworth into the operation, he testified, and started asking his friend questions to "probe possible larceny in his heart."

In 1974, over drinks at Boom Trencherd's Flare Path restaurant at the San Diego airport, Walker testified, he revealed that he was selling classified information and told Whitworth that "I could build him into the sale."

Walker testified that he told Whitworth his buyers were "possibly organized crime, the Mafia, allied countries such as Israel or private organizations such as the publication Jane's Fighting Ships." He said he never made clear exactly where the material was going.

In his testimony, Walker described how Whitworth would use a miniature Minox camera to photograph Navy cryptographic material and messages, sometimes in the secrecy of the "crypto vault" aboard a ship where Whitworth was supposed to be responsible for the security of such coding material, sometimes in a van the Soviets bought him as a bonus for good performance.

Walker's testimony was supplemented by seized by government agents, including telephone records, calendars listing meetings and drops, travel receipts, and "payment schedules" listing money Whitworth received from Walker.

Government experts in codes and communications testified that the material Whitworth provided would have permitted the Soviets to eavesdrop on supposedly secure Naval communications.

Defense lawyers Larson and Tony Tamburello called as witnesses John Walker's daughter, Margaret Walker, and his half-brother, Gary Walker, as well as Laurie Robinson, Walker's partner in his private detective agency.

Robinson testified that Walker told her he could "make up stories" about the spy ring to tell the government.

Whitworth's friend and sailing companion, Roger Olson, described Whitworth in testimony as "one of the most patriotic Americans that I have ever known." John Walker, he said, "would sell out his own mother."