Retired Navy communications specialist Jerry Alfred Whitworth, whose trial on espionage charges opens here Tuesday, spent large sums of cash shortly after he allegedly received payments from convicted spy John Anthony Walker Jr., a federal prosecutor said today.

Assistant U.S. Attorney Leida B. Schoggen said the government would seek to show at Whitworth's trial that, in a one-month period after he allegedly received $100,000 from Walker in June 1980, Whitworth made cash purchases totaling more than $15,000, including a $1,218 videocassette recorder he bought within a few days of the alleged payment.

In the three months after he allegedly received the money from Walker, Schoggen said, Whitworth spent $30,000 in cash. "During this time, his salary wasn't even close to $30,000 a year," Schoggen said.

Schoggen described the purchases in opposing a motion by Whitworth's attorneys to have the eight espionage charges against him tried separately from five tax counts.

Jury selection is scheduled to begin Tuesday for Whitworth, 46, the last of four Navy men charged in the Walker espionage ring to face trial.

Whitworth, who was a senior chief radioman when he left the Navy in 1983, is charged with conspiring to commit espionage with Walker from 1974 until Walker's arrest May 20 of last year, and with passing him highly sensitive information about Navy codes. Walker pleaded guilty Oct. 28 in Baltimore federal court to spying for the Soviet Union and is scheduled to testify for the prosecution here.

In asking that the tax counts be severed from the espionage charges, defense attorney James Larson told U.S. District Judge John P. Vukasin Jr. that Whitworth wants to testify about the espionage charges but not about the tax charges. He submitted a sealed statement from Whitworth that he said would explain Whitworth's reasons.

Vukasin said he agreed with the government that the two sets of charges are related, but he deferred ruling on severing the charges until he had read Whitworth's statement.

He also postponed ruling on whether the government can introduce four letters signed simply "RUS" that were sent to the FBI's San Francisco office in 1984 and offered to expose "a significant espionage system." The government contends that Whitworth wrote the letters.

Vukasin has so far refused to permit the letters to be used at the trial, saying that the government had not presented sufficient proof they were written by Whitworth and terming the letters "in essence confessions" that would virtually eliminate the need for a trial.

Vukasin said today that the similarities between the espionage ring described in the "RUS" letters and the Walker ring in which Whitworth allegedly participated were "like pieces in a jigsaw puzzle. They all seem to fit."

He expressed concern, however, that the letters might be "unduly prejudicial" against Whitworth.

In arguing that the counts of failure to report income and tax fraud should be tried together with the espionage charges, Schoggen also said that Whitworth spent more than $16,000 in a 10-day period in February 1983 when he flew back to California from the Philippines, where he was stationed aboard the aircraft carrier USS Enterprise. She said his purchases in one day totaled $1,400, including a $393 Sony Walkman radio.