Charles Hayes received permission to give out his CIA control number and file name, which he did. However, the prosecution made no attempt to verify this. This may be a basis for an appeal.
The judge refused to allow testimony from a CIA employee who was scheduled to testify about the FBI falsifying evidence, and who could have verified that Hayes worked for the CIA.
Hayes had not intended to use his employment with the CIA as his defense. However, the prosecution got the jury to dismiss Hayes' credibility based on the lack of evidence that Hayes worked for the CIA. Since testimony on Hayes' CIA background was disallowed, the Fifth Column story, which was introduced in the context of his CIA background, was also discredited.