The trial of three anti-Castro Cuban exiles charged in connection with the 1976 car bombing assassination of former Chilean ambassador Orlando Letelier evolved into a day-long series of private legal wrangles yesterday, while the jury only heard 40 minutes of testimony from Letelier's widow.

The chief problem arose because precise translations had not been prepared of Letelier's correspondence in Spanish that was found in his briefcase in the wreckage of his car that was blown up along Washington's Embassy Row.

Assistant U.S. Attorney Eugene M. Propper questioned Isabel Letelier yesterday afternoon about the events that led to her husband's assassination on Sept. 21, 1976. But then U.S. District Judge Barrington D. Parker sent the jury of seven women and five men back to the local hotel where they are sequestered. He said that Mrs. Letelier would be cross-examined by defense attorneys this morning.

In a private bench conference and at a later session in a room behind Parker's courtroom, defense lawyers said they were particularly interested in asking Mrs. Letelier about four letters found in the briefcase.

The correspondence included a letter from ousted Marxist Chilean President Salvador Allende to Letelier; a Letelier letter to Allende's daughter, Tati; a Letelier letter to Cuban foreign minister Raul Roa and a letter to Letelier from a German branch of Letelier's political party, the United Popular Movement.

Because precise translations had not been prepared of the documents, Parker directed Oscar Suarez, a Spanish-speaking defense lawyer in the case, and two Spanish-speaking FBI agents to jointly prepare a translation.

In addition, defense lawyers asked Parker to strike the testimony Tuesday of Sen. George McGovern (D-S.D.) on grounds that nothing Letelier told McGovern in 1975 conversations ever reached Chile or the Chilean secret police, known as DINA.

McGovern had testified that Letelier had "sensitized" him to the issue of alleged human rights violations in Chile, as to a possibly contributing factor in providing a motive to why DINA officials allegedly ordered Letelier's assassination.

Parker did not rule on the motion to strike McGovern's testimony.

Meanwhile, the prosecutors in the case asked Parker to prohibit the defense attorneys from repeatedly asking prosecution witnesses about the alleged involvement of the Central Intelligence Agency in the slaying of Letelier. The defense has contended that the CIA ordered the slaying of the former diplomat, while the prosecution has laid the blame at the doorstep of DINA.

Mrs. Letelier wore a neckalce yesterday containing a black stone carved with her nickname "Isa" by her husband while he was imprisoned by the military dictatorship of Gen. Augusto Pinochet after the coup deposing Allende. She testified that she was not told for three months after her husband's arrest during the September 1973 coup where he and other Allende government officials and supporters were being held.

By the time she saw him in February 1974, she said, "he looked horrible" and had lost 40 pounds. Asked if he eventually was released by the Pinochet regime, she replied, "He wasn't released. He was expelled from the country."

She recounted his repeated attacks on the Pinochet regime after he came to U.S., his lobbying efforts against the Pinochet government with prominent U.S. lawmakers and his eventual assassination.

She said that on the day of assassination she had made plans to have lunch with her husband. But when she was called to George Washington University Hospital and saw friends there, she said, "I could see from their faces something terrible had happened."

Ronni K. Moffitt, a colleague of Letelier at the Institute for Policy Studies, was also killed in the blast. Two of the Cubans on trial, Guillermo Novo Sampol and Alvin Ross Diaz, are charged with the two killings, while the third defendant, Ignacio Novo Sampol, is charged with lying to a grand jury investigating the slayings.