In what circumstances will a trial judge refuse to exclude evidence of prior crimes from a defendant's testimony?

It is true that Palumbo stands for the proposition that a trial judge has discretion to exclude evidence of prior crimes in an appropriate case and to decide to do so in advance of defendant's testifying. However, while such a practice may sometimes be desirable, Palumbo does not suggest, as appellant would have us rule, that it is necessarily error for the judge to defer exercising that discretion until the defendant has in fact testified. Indeed, in Palumbo itself, we stressed that the trial judge has discretion in this area, see 401 F.2d at 274, and we have subsequently approved a district court's discretionary refusal to make advisory rulings in similar circumstances. See United States v. Evanchik, 413 F.2d 950 (2d Cir. 1969); United States v. Hart, 407 F.2d 1087, 1088-1089 (2d Cir. 1969). Under these circumstances, we hold that there was no abuse of discretion in the trial judge's failure to make an anticipatory ruling.