Testimony ended today in the trial of accused spy Arthur James Walker after the defense rested without putting on any evidence, and Walker's lawyers conceded that prospects for a complete acquittal were grim.

"Mentally, he's prepared for the fact of conviction" on at least some of the seven counts of espionage, defense lawyer Samuel Meekins said after court today. Walker "hasn't given up hope," but "he seems to be in the resignation stage."

J. Brian Donnelly, Walker's other defense lawyer, said his client had chosen not to testify or to call any other witnesses because, "We just didn't think it would add to the case . . . . I think Arthur's said enough."

A retired lieutenant commander, Walker, 50, is the first of four Navy men charged with passing defense secrets to the Soviet Union to stand trial.

Meanwhile, one of the other defendants, retired Navy Chief Petty Officer Jerry Whitworth, pleaded not guilty in a San Francisco courtroom today to a 12-count indictment accusing him of spying for the Soviet Union and evading federal taxes on $332,000 he allegedly received for turning over the information.

Closing arguments are scheduled tomorrow in the trial here, in which prosecutors presented 35 witnesses over four days. U.S. District Judge J. Calvitt Clarke Jr., who is hearing the case without a jury at Walker's request, could render a verdict as early as Friday.

Walker is charged with receiving $12,000 from his younger brother, John Anthony Walker Jr. -- who is accused of masterminding the alleged spy ring -- in exchange for classified documents from VSE Corp., a Chesapeake, Va., defense contractor where Arthur Walker worked as an engineer. If convicted on all counts, he faces a total of three life sentences plus 40 years in prison.

Much of the evidence in the case came from Walker himself, who gave detailed statements to the FBI and to a federal grand jury in Baltimore about his brother's alleged espionage activities and his own participation.

Little of today's testimony focused on Arthur Walker, a balding, bespectacled man who appears far from the classic image of a Soviet spy.

But it provided the first public glimpse of John Walker's alleged Soviet "handler," embassy Vice-Consul Aleksey Gavrilovich Tkachenko, and details of his abrupt departure from the United States three days after John Walker's arrest May 20 at the Rockville Ramada Inn.

The acting resident manager of Tkachenko's Alexandria apartment complex testified that the Soviet diplomat vanished so quickly after Walker's arrest that he left food rotting in the refrigerator and an apartment full of furniture, including a bedroom mirror bearing a "President Reagan: Bringing America Back" bumper sticker.

Tkachenko, a dark-haired, dour-looking man in a State Department photograph admitted into evidence today, was spotted by FBI agents May 19 near the rural Montgomery County "drop site" where John Walker is alleged to have left a bagful of classified Navy documents.

Tkachenko never retrieved the bag, and there was no testimony today explaining the Soviet official's failure to do so.

But FBI agent Stephanie Gleason said she spotted Tkachenko, his wife Olga and their two daughters arriving at National Airport about 10:25 a.m. on May 23. The family, she said, was accompanied by three Soviet "escorts," one of whom boarded the plane with them and later got off.

Today's testimony also added new details of "tradecraft," the complicated methods by which John Walker and his Soviet handler left packages for each other at remote "dead drops" or met overseas.

Prosecutors introduced the contents of a manila envelope dropped by John Walker when he was arrested by FBI agents that contained detailed maps and photographs directing him to the rural roadside drop site in Poolesville, Md., and listing various signals to indicate that the operation was proceeding as planned.

The photographs of spots along the way were marked with arrows and directions such as, "You drop your final can here," apparently referring to the soda cans that were used as signals.

Prosecutors also introduced a map and document, labeled "The Vienna Procedure," seized from John Walker's Norfolk home and giving what an FBI counterintelligence expert testified were detailed instructions for a face-to-face meeting with Walker's Soviet counterpart.

"For easy identification please carry your camera bag on your left shoulder and a small paper bag in your right hand," states the document, written in neat block printing with street names marked in red. It instructed Walker exactly what shop windows to browse in, and for how long, before the Soviets would make contact with him.

Gerald Richards, an FBI specialist in Soviet "tradecraft," testified that he believed the Montgomery County and Vienna instructions had been prepared by the same person or persons, and that they both bore the marks of Soviet handiwork.

"Nobody does it quite as well as they do," Richards testified.