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

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 re-analyses 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.