Monday, March 19, 2012
Using ideas rooted in fact-finding accuracy, courts hold that defendants open the door to illegally-obtained evidence when they use exclusion as a "sword" to offer contradicted evidence or arguments. Yet the metaphor holding that rules excluding evidence can function "as shield, but not a sword" is inapt when applied to rules that promote non fact-finding goals. Whether the door is opened to admission of evidence excluded by such rules must depend on a contextual analysis of the rule's purpose. Finding that defendants cannot use the constitutional exclusionary rule to advance contradicted evidence or argument negates its necessary deterrent function. Defendants should lose immunity against illegally-obtained evidence only when they offer evidence derived from the same unlawful search or interrogation, or ask the jury to consider why the prosecution did not produce the suppressed evidence. The waiver rule allows the exclusionary rule to accomplish its purpose while protecting the integrity of our fact-finding process, which occasionally values social goals above fact-finding accuracy. By distinguishing arguments about the absence of suppressed evidence from those equivalent to assertions by witnesses required to lie about events to prevent jurors from learning of suppressed evidence, the waiver rule protects jurors from the assault on rational autonomy to which Kant objected. Whether Kant would find sufficient evidence law’s respect for jurors’ right not to be lied to or insist upon their right to all available evidence, we cannot expect evidence rules to function without limiting the evidence that jurors consider. As long as we do, courts must assure that their decisions about opening the door do not undermine the goals that exclusion is designed to achieve.