The trial of Arthur J. Walker on charges of espionage began here today with testimony that Walker told FBI agents he was drawn into the spy ring by his brother because he needed money.

According to an FBI agent's testimony and FBI documents released today, Walker, 50, a retired Navy lieutenant commander, told authorities he was first drawn into the spy ring about 1980 after the failure of a business venture with his brother, alleged spy ringleader John A. Walker Jr.

Arthur Walker said he had suspicions that his brother was engaged in illegalities as far back as the late 1960s, but was not certain until his brother told him about 1980 of dealings with "people in Europe," according to testimony by FBI special agent Barry D. Colvert and FBI documents.

Arthur Walker's descriptions of his dealings with his brother come from conversations he had with FBI agents on May 20 -- the day John Walker was arrested on espionage charges in Rockville after allegedly leaving documents for a Soviet diplomat in rural Montgomery County -- and in the days afterward.

Defense attorneys have asked that these talks be withdrawn as evidence because they say Arthur Walker was told he would not be prosecuted if he gave information. U.S. District Judge J. Calvitt Clarke Jr. again rejected that argument today.

Arthur Walker faces seven counts, including conspiracy to commit espionage, for which he could receive three life sentences plus 40 years. The three others to be tried in the case -- retired Navy Chief Warrant Officer John Walker, 48; his son Navy Seaman Michael L. Walker, 22; and John Walker's friend Jerry A. Whitworth, 45 -- will be tried later.

When first confronted by the FBI hours after John Walker's early- morning arrest May 20, Arthur Walker said he knew nothing of his brother's espionage, according to Colvert's testimony. He spoke repeatedly and at length with FBI agents, and each time gave more information, especially after he failed a polygraph test.

He repeatedly said he did not need a lawyer, even though FBI agents told him he "would be a fool" if he were guilty of espionage and continued talking to them, Colvert said.

Arthur Walker told the FBI he was "truly down in the dumps" because of financial problems in January 1980, when he and brother John took a drive in Norfolk and John told him, "I have friends who will pay for classified information."

Arthur Walker told the FBI that he took a job with VSE Corp., a Chesapeake defense contractor, to gain access to classified information.

According to the FBI, Arthur Walker said that over the next few years his brother told him in detail about his espionage -- how he photographed documents, "dead drops" where he left material for the Soviets, trips to Vienna to meet intelligence agents, and even how he strapped a money belt on their aged mother during a trip to Europe to transport the money into the United States.

John Walker first got into contact with the Soviets years ago, apparently in the late 1960s while he was an active duty Navy officer, by sitting in a car near the Soviet Embassy on 16th Street NW in Washington, an FBI report quoted Arthur Walker as saying. The Soviets later contacted John Walker, his brother said.

Arthur Walker decided to waive a jury trial and instead have Judge Clarke determine the verdict to "take the emotion out of the trial," said one of his lawyers, Sam Meekins. He added that prosecutors "have the emotion on their side," especially given the many Norfolk area residents with connections to the Navy.

Meekins added that he thought jurors might have feared a backlash from friends and family if they did acquit Arthur Walker.

Before the trial began, defense and prosecution attorneys briefly discussed a plea bargain, but the negotiations were unsuccessful, Meekins said.

In opening arguments, Walker's other lawyer, J. Brian Donnelly, said that evidence was insufficient to show John Walker was a Soviet agent in 1981 when, it is charged, Arthur Walker gave him documents to be passed to the Soviets.

Donnelly added there is no evidence Arthur Walker's material ever went to Soviet intelligence agents, and said the defense "will require the government to prove damage was done to the United States."

Military analysts in recent interviews have said the information Arthur Walker allegedly passed was the least significant of the material supposedly compromised in the case involving the four men.

Arthur Walker is charged with passing two documents -- classified "confidential," the least sensitive category -- from his employer, VSE Corp. where he worked as an engineer. He has acknowledged receiving $12,000 from his brother John for the information.

Prosecutors charged that in 1981 Arthur Walker lent his brother a "damage control book," a training manual on repairing damage on a Navy ship. It is also charged that in 1982, Arthur Walker passed on a report on equipment failures aboard amphibious vessels.

Yesterday, Assistant U.S. Attorney Tommy Miller described these documents as "critical," and added they could tell the Soviets about Naval combat readiness.

Arthur Walker told the FBI that his brother continually nagged him in the early 1980s about getting sensitive documents from VSE, and kept sending him back to find secret material.

Colvert said Arthur Walker told him that he sometimes exaggerated his access to secret documents so that John Walker would continue paying him money.