It's negotiating for testimony in the first place. Starr's fondest wish, of course, is to have Lewinsky testify that Clinton and his cronies not only lied under oath about the president's sex life, but obstructed justice and suborned perjury by trying to convince witnesses to lie. The bidding was overt and hard-nosed. Reportedly, Lewinsky was willing to go so far as to admit that she and Clinton had had sex, but was unwilling to say that Clinton had asked her to lie about it. Yet Starr, it was said, held out for the most damning testimony.
Memory has a way of being clouded by fear.
Crossen apparently forgot that he was no longer a fed. After all, they put potential witnesses under the most severe pressure - the threat of doing time in federal prison. And there is no principled difference between pressuring or threatening a witness into testifying for the prosecution and doing the same to induce testimony for the defense. It's that simple. Even when the victims of these techniques complain to judges, the judiciary turns a deaf ear.