The problem, the court held, was the possibility that witnesses against the defendant might have seen his immunized testimony on television and allowed it to taint their own trial testimony.

Mr. Walsh had gathered most of his evidence before Mr. North gave his immunized testimony.

Although McFarlane completed his grand jury testimony before North gave his immunized testimony, McFarlane was key Government witness at trial.

According to Judge Gesell's reasoning, the only way to allow the immunized testimony to be used at trial without infringing on the rights of the defendants is to try them separately.

If prosecutors can compel defendants to provide these kinds of evidence, they should also be allowed to introduce reliable evidence that is found as a result of earlier immunized testimony.

His conviction was later overturned on grounds that he did not receive a fair trial (the prosecution may have been influenced by his immunized testimony in front of Congress.)

His convictions were later overturned on the grounds that his immunized testimony had tainted his trial.

But each of the defendants has the right to use the immunized testimony of others in presenting his defense, and they have all said they would do so.

In the appeal, Mr. Walsh said the appeals court had erected obstacles "of unprecedented strictness to the prosecution of persons who have given public immunized testimony."

A year later, a Federal appeals court threw out the convictions because his immunized testimony had been improperly used against him.