Can defense counsel question or comment in closing argument on the ramifications that testifying against prison guards could have on parole and safety within the prison?

The district court refused to allow defense counsel to question inmate witnesses, or comment in closing argument, on the ramifications that testifying against prison guards could have on their parole and safety within the prison. The government asserts that the imposition of such restrictions was proper and within the district court's discretion because the substance of what defense counsel sought to introduce into the record was irrelevant. The scope of the examination of a witness, like the conduct and content of counsels' closing argument, is determined by the trial court in the exercise of its discretion. See Herring v. New York, 422 U.S. 853, 862 (1975). In the instant case, however, the court abused its discretion.