This discussion about the fibers reminds me of the 911 tape where they had Patsy in for questioning and told her "It's there" meaning that there was conversation on it after she had supposedly hung up. She asked them to play the tapes, but they didn't do it because they knew that she wouldn't hear any conversation. Lin did exactly the right thing here, and so did Patsy when she asked them to play the tape.

I believe that these are both cases of illegitimate and counterproductive interrogation technique, failed attempts to get the witness to say something ON RECORD, even if it's pure speculation based on misrepresentations of the known facts. The witness' speculations, if they are provided for the record, can be used later during cross-examination at trial in an attempt to discredit the witness. This isn't the best way, probably not even a good way, to get at the truth. This is setting people up for further "persecution," not an "investigation."