THE INDEPENDENT REVIEW PANEL which investigated CBS News’s faked memos found no basis to accuse Dan Rather or Mary Mapes of political bias in connection with their roles in the offending 60 Minutes story about President Bush’s National Guard service. In its report the Panel characterized the very question of whether a political agenda could play a role as “subjective” and “difficult.” And panelist Louis Boccardi later explained that “bias is a hard thing to prove.”

Yet questions about motivation lie at the heart of many garden-variety legal disputes, most notably cases involving issues of unlawful discrimination under various civil rights statutes. Recognizing that very few employment decision-makers will admit to bias, the Supreme Court quickly developed a construct for inferring the existence of bias through “indirect” evidence. Proving bias thus became no more difficult than proving other allegations of fact, a state of affairs consistent with Chief Justice Rehnquist’s comment that the state of one’s mind is just as much a factual issue as the state of one’s digestion.