Criminology Expert Witness

A criminology expert witness provides independent specialist opinion on crime, criminal behaviour, criminal justice systems and the processes through which offences are investigated, prosecuted and tried. Criminology draws upon sociology, psychology, law, statistics, public policy and criminal justice research.

Experts in this field are often senior academics, researchers or practitioners, including Professors of Criminology or Criminal Justice, Readers, Associate Professors and doctorate-level specialists. The appropriate expert should have demonstrable expertise in the specific issue before the court, such as jury decision-making, criminal procedure, policing, sentencing, prisons, offending behaviour, criminal justice policy, miscarriages of justice or statistical analysis.

Criminologists are most commonly instructed in criminal proceedings where specialist empirical or academic evidence is required. One important area is jury behaviour and potential jury bias. An expert may analyse established research concerning jury composition, racial or demographic bias, juror comprehension, judicial directions, pre-trial publicity, internet exposure, sexual offence myths and misconceptions, and the factors that may influence group decision-making.

A criminologist should not determine whether a particular jury was biased or speculate about private jury deliberations. Instead, their role is to explain what reliable research demonstrates, identify methodological limitations and distinguish evidence-based conclusions from assumptions or speculation.

Experts may also be instructed concerning patterns of offending, criminal justice disparities, police or institutional practices, sentencing trends, prison systems, rehabilitation, recidivism, desistance and miscarriages of justice. They may assess whether propositions advanced in proceedings are supported by recognised criminological evidence.

The work is usually documentary and research-based. Material reviewed may include the letter of instruction, indictment, prosecution and defence case statements, witness statements, trial transcripts, judicial directions, sentencing remarks, appeal judgments, police or CPS policies, prison or probation records, published research, official statistics and relevant datasets.

A criminology expert report should clearly identify the expert’s qualifications, instructions, documents considered, methodology, research relied upon, findings, limitations and conclusions. Where academic opinion is divided, the expert should identify the range of reasonable opinion and explain why their own conclusion is preferred.

Relevant terminology may include jury representativeness, implicit bias, explicit bias, base rates, statistical significance, effect size, correlation, causation, confounding variables, selection bias, recidivism, desistance, criminal careers, institutional practice and empirical evidence.

In criminal proceedings in England and Wales, expert evidence must comply with Part 19 of the Criminal Procedure Rules. The expert’s duty is to assist the court objectively and independently, regardless of which party has instructed or paid them.

Where criminological expertise is required in civil litigation, CPR Part 35 and Practice Direction 35 apply. The expert’s overriding duty remains to the court, and evidence must be confined to matters within the expert’s expertise.

A criminologist might be asked whether UK research supports an allegation of jury bias, whether overseas jury studies can properly be applied to English Crown Court proceedings, whether criminal justice statistics support an asserted disparity, or whether the methodology of research relied upon by another party justifies its conclusions.