Development of evaluative opinions

Sets out a standardised approach to formulating evaluative opinions used by forensic scientists in the criminal justice system.



This appendix has been prepared to:

  • promote improvement and standardisation in the development of evaluative opinions
  • improve alignment between disciplines
  • encourage development of better data sets to inform interpretation
  • encourage better design and use of proficiency trials to calibrate expert performance
  • enhance the transparency and understanding of opinion evidence in the courts

It considers the Casework Assessment and Interpretation (CAI) model and in particular addresses issues around:

  • formulating hypotheses at the appropriate level
  • how to proceed in the event of a ‘No Comment’ defence
  • interpretation where there is limited or no data
Published 11 February 2021