Middle Eastern students stole a sample from ISU in 1990.
There is a LOT of very damning evidence in it - more than enough to convince almost any jury. And, contrary to what some people seem to believe, circumstantial evidence IS valid and usable in court. In fact, most cases that go to trial depend entirely on circumstantial evidence. If there are movies of the crime being committed, or if there's a confession, there usually is no need for a trial. Plea bargaining eliminates the need.
Ivins' lawyer may think there isn't enough evidence to convict, but that's his job. Rush Holt may want more, but he's a politician who evidently sees some political reason to question the FBI's findings.
I hope that Holt gets his commission to investigate the investigation. It can only make the solid evidence against Dr. Ivins more clear to the world.