Yes, that study was done in the early eighties, and in that study only 9% of the trial judges indicated that mandatory minimums never affected their ability to impose a just sentence. So the converse of that would arguably be true, which is that 91% of judges felt that at least some of the time their ability to impose a just sentence was being affected by a mandatory minimum.
This study was repeated in a 2001 article by Anthony Doob. I believe he is appearing before the committee, so I'm sure he will be able to provide additional information.