Defining 'reasonable medical certainty' in court: What does it mean to medical experts in child abuse cases?

Physicians and others who provide expert testimony in court cases involving alleged child abuse may be instructed to state their conclusions within a 'reasonable medical certainty' (RMC). However, neither judges nor jurors knows what degree of probability constitutes RMC for a given expert, nor whether different experts use different standards to formulate their opinions. We sought to better understand how experts define RMC in the context of court cases. An email survey was sent to members of six list-serves, representing four specialties, whose members testify in child abuse cases. Respondents were asked to define how RMC corresponded to (1) the numerical probability that abuse occurred, (2) the ordinal probability, and (3) how their determinations relate to common legal standards ('preponderance of the evidence', 'clear and convincing', and 'beyond a reasonable doubt'). Participants were also asked how comfortable they were in defining RMC; whether their definition changed according to the charges or type of proceeding; and how they would apply RMC to several hypothetical cases. The 294 list-serve participants who responded included child abuse pediatricians (46%), forensic pathologists (21%), pediatric neurosurgeons (15%), pediatric ophthalmologists (12%), and others (6%). Though 95% of respondents had testified in court, only 45% had received training in the definition of RMC. Only 37% were comfortable defining RMC. Although many responses were highly clustered and paired comparisons showed that 95% of participants' responses were internally consistent, there was variability in respondents' definitions of RMC. There is some variability in how child abuse expert witnesses define and use the term RMC; we provide suggestions about how to more accurately and transparently define RMC to ensure justice in these cases.