Is the leniency asymmetry really dead? Misinterpreting asymmetry effects in criminal jury deliberation

Abstract

Early jury simulation research, reviewed and meta-anyalysed by MacCoun and Kerr (1988), suggested a leniency asymmetry in criminal jury deliberations such that a given faction favoring acquittal will tend to have a greater chance of prevailing than would an equivalent sized faction favoring conviction. More recently, a handful of field studies of actual juries have reported either no such leniency asymmetry or one in the opposite direction (a severity asymmetry). A potential bias in the coding of these field studies' data is identified, one that would tend to underestimate any leniency asymmetry. The data from three field studies are re-analyzed after correcting this purported coding bias. The results of these reanalyses show a leniency asymmetry effect, although one that is less pronounced than observed in mock jury studies. It is argued that this difference in degree (not existence) of leniency asymmetry can plausibly be attributed to greater imbalance in evidence strength in the typical actual trial relative to the typical stimulus case in simulation experiments. It is also noted that failure to observe such a leniency asymmetry effect in actual juries would raise important questions about their adherence to the reasonable doubt standard of proof.

Balancing evidence and norms in cultural evolution

“…3 In the deliberation paradigm, group members in opposing factions (arbitrarily labeled sources vs. target) influence each other in a bidirectional fashion. bBOP fits these data better than several other influence models examined by MacCoun (2012) -in particular, it captures the profound asymmetry that is consistently seen in mock criminal jury data (Kerr & MacCoun, 2012;MacCoun & Kerr, 1988; for example the data for 12-person mock juries presented in Panel c; also see Fig. 4 discussed below).…”

“…4 (adapted from MacCoun, 2014) shows data from 9 different mock and real criminal jury studies, as well as 7 different studies using ''intellective'' group tasks with a demonstrable correct answer, plotted in the bBOP parameter space. Note that the two regions do not overlap; groups working on intellective tasks share an asymmetric threshold that enables good minority solutions to prevail; criminal juries operate under some asymmetry (favoring acquittal) but with greater clarity, as might be expected given that they are instructed to apply a ''beyond a reasonable doubt'' standard (Kerr & MacCoun, 2012;MacCoun & Kerr, 1988).…”

“…The sigmoid shape implies that factions can have disproportionately more or less influence than one would predict from their relative size. But the BOP models readily allow for considerable asymmetry in the threshold, and I have argued that this asymmetry is an essential feature of actual choice and influence behavior (also see Kerr & MacCoun, 2012;MacCoun & Kerr, 1988).…”

Scientific inquiry on how groups decide: The Davisonian approach

“…We finally settled on starting with papers with the strongest or most direct links with Jim's own substantive work and finishing with those that explored aspects of "how groups decide" that were more distant from Jim's usual interests. The first paper, by Kerr and MacCoun (2012), examines a phenomenon that Jim Davis speculated about in his original SDS paper (Davis, 1973), and subsequently confirmed empirically , Davis, Stasser, Spitzer, & Holt, 1976. He called it the "defendant protection norm"-a tendency for pro-acquittal factions in criminal juries to prevail more often than comparable pro-conviction factions.…”

Accentuation of bias in jury decision-making

“…Note that this case strength moderates leniency asymmetry as well. As MacCoun and Kerr (1988;Kerr & MacCoun, 2012) pointed out, leniency asymmetry would be attenuated for cases wherein the evidence against the defendant is clearly strong. These findings alert us not to assume the effect of jury deliberation (e.g., bias accentuation/attenuation, leniency asymmetry) as some kind of universal constant, but to identify the moderating factors behind it (e.g., case strength) with a "contingent" perspective.…”