The conflict between precision and flexibility in explaining "beyond a reasonable doubt"

Though beyond a reasonable doubt is a common phrase inside and outside the courtroom, courts have struggled to define the phrase or to set clear standards for an adequate definition. The struggle has important implications because empirical evidence reveals that the choice of definition can influence the jury's verdict. The authors analyze the variety of proposed definitions, including the quantified definitions that some have advocated, setting out 5 criteria for an adequate definition consistent with both legal requirements and empirical evidence. They also suggest that the push for precision, such as that promised by a quantified definition in the form of a single percentage, may produce a loss of desirable flexibility. A structured flexibility permitting the trier of fact to adjust the stringency of the standard to reflect the severity of the offense and the costs associated with error may be a virtue worth fostering.