Ruling in North Case Rested on Two Traditions : Law: A person may be compelled to testify but his forced testimony can’t be used against him. The prosecutor had opposed Congress hearings.

Forcing a witness to testify in public about criminal wrongdoing represents a clash between two traditions in English and American law. Throughout U.S. history, judges have had the power to force reluctant witnesses to appear in court. Grand juries investigating crimes could not operate if all witnesses could simply refuse to talk.

But the Constitution protects such reluctant witnesses from being punished for what they say. “No person . . . shall be compelled in any criminal case to be a witness against himself,” the Fifth Amendment says.

For one week in July of 1987, Congress forced Lt. Col. Oliver L. North to testify before the nation on his role in the Iran-Contra affair.

And, on Friday, a U.S. appeals court concluded that independent counsel Lawrence E. Walsh had failed to meet what it described as the “heavy burden” of proving that nothing North said was used against him.

In the 1972 case of Kastigar vs. U.S., the Supreme Court set down rules to reconcile the conflict between forced testimony and forced self-incrimination. If the government forces a witness to testify, it may later prosecute him, but it may not use anything that he disclosed in his forced testimony.

Moreover, prosecutors have “an affirmative duty to prove” that all the evidence used in the trial is “wholly independent” of what was disclosed by the reluctant witness.

For Walsh and his team of prosecutors, the Friday ruling is another frustrating setback. In January, 1987, Walsh urged congressional committees not to force North and other Iran-Contra witnesses to testify, saying that it would “create serious and perhaps insurmountable barriers to the prosecution” of those witnesses.

When Congress went ahead, Walsh and his team tried to shut their eyes and ears to what was said. For weeks, they were under orders not to watch television, read the newspapers or discuss North with friends or family.

But that was not enough, the appeals court said. In the Justice Department, the White House and the CIA, officials watched the North hearings on TV and then they appeared before a grand jury to testify about the Iran-Contra scandal. Their testimony was therefore “tainted,” the appeals court said.

“A sizable number of grand jury witnesses, trial witnesses and their aides apparently immersed themselves in North’s immunized testimony . . . (and may have had) their memories refreshed,” the appeals court said. If this is so, the appeals court said, North’s conviction would be based in part on his forced testimony, a violation of his Fifth Amendment rights.

But the appeals court did not finally settle the matter. It ordered the trial judge, Gerhard A. Gesell, to hold another hearing to give prosecutor Walsh a chance to prove that his case is entirely untainted by the North testimony.