The Ninth Circuit here upholds former Ninth Circuit Jury Insruction No. 4.11 -- currently replaced by No. 4.9, which says essentially the same thing -- which advises the jury that it should consider the testimony of defendat's alleged accomplice on his behalf "with greater caution than that of other witnesses." Judge Wardlaw holds that the instruction is proper because the accomplice might well be committing perjury in order to exonerate his accomplice (and, by extension, himself).
On this same theory, shouldn't we also give an instruction that the jury should view defendant's own testimony with similarly "greater caution," since he's got an equal -- indeed, greater -- incentive to lie? We don't do so, and I think a lot of people would find such an instruction to be constitutionally infirm. But it's hard to distinguish the two directives.
Judge Wardlaw's opinion isn't surprising, and it's consistent with the holdings of the Fifth and Seventh Circuits. But it's still a little bit troubling.