Forensic Science and Jury Decision-making

Analysing the weight of forensic language used in court, in order to ensure the most accurate use of fornesic evidence.

Forensic language large


  • Dr Sarah Cooper
  • Dr Paraic Scanlon

Research background

In the US, unreliable forensic science evidence is a known cause of wrongful conviction. Dr Cooper’s research examining US court responses to scientific uncertainty, identified that some courts have addressed alleged uncertainty in firearms identification evidence by restricting expert testimony, including by instructing experts to not testify in absolute terms, such as “there is an exact match,” but rather in allegedly more diluted terms, such as a match can be made “more likely than not” and “to a reasonable degree of certainty.” Jurors, who generally lack scientific expertise, must determine the weight of such evidence in criminal trials, yet there is limited knowledge about how they interpret specific expert phrases. Since 2016, Dr Cooper and Dr Scanlon have been using their respective expertise in law and psychology to design and co-ordinate mock juror studies that investigate this gap in knowledge.

Research aims 

This research generally to investigate the levels of certainty jurors attach to common expert phrases, with a view to identifying ways to support agents in the legal process to make the most accurate use of forensic science evidence.

Research methods

The research is typically carried out using an online questionnaire, with participants asked to rank their level of certainty of various expert statements, on a scale of zero to one hundred. Participants are generally recruited via academic, professional, and community links across the US, and are screened against the eligibility criteria to sit on a federal jury. The data collected is statistically analysed.


Dr Cooper and Dr. Scanlon have published their findings and disseminated their research at practitioner conferences in the US and at the European Association of Psychology and Law annual conference. The study series has been supported by multiple Faculty Small Development Grants, funding numerous students to collaborate with the academic team.