Metrics of Mayhem: Quantifying Capriciousness in Capital Cases

Abstract

Social science has figured prominently in debates over the constitutional administration of capital punishment for more than a half-century, especially with respect to capricious and bias decision-making. Yet the weight given to this empirical evidence (or lack thereof) in judicial decision-making has, itself, been irrational and inconsistent. A key obstacle for litigants and scholars raising empirically anchored claims of capriciousness has been the absence of a workable definition from both capital statutes and the courts’ analysis of them. How is this phenomenon to be measured and what threshold showing must be made before these claims of constitutional error become cognizable to the Court? The science of statistics, at its core, is concerned with drawing inferences from data in the face of various types of uncertainty, and therefore provides a useful framework for identifying and quantifying the types of errors relevant to the assessment of the constitutionality of the operation of death penalty systems. In other words, statistical social science facilitates the measurement of the extent of mayhem in capital charging-and-sentencing that the Court has, in theory, labored to minimize for the past five decades. The purpose of this essay is to describe several statistical techniques that are capable providing doctrinally-relevant and empirically-informed assessments of the degree of capriciousness in capital charging-and-sentencing systems that can be “scrutinized [by the Court] with greater care than it had done it the past.”

Keywords: death penalty, capital punishment, capriciousness, Eighth Amendment, cruel and unusual punishment, social science