The Latest Guidance on Expert Reports from England's Forensic Science Regulator

This week, the Forensic Science Regulator for England and Wales issued a third version of guidance on the content of expert reports for criminal cases. Forensic Science Regulator, Guidance on the Content of Reports Issued by Expert Witnesses in the Criminal Justice System in England and Wales, Apr. 17, 2019.

 These reports are required "when the witness will, either in the report or in testimony at court, provide evidence of opinion." Some items are rather mundane -- for instance, a report must be signed by its author. But several parts of the guidance are noteworthy:

• The author must certify that the report is truthful and, if introduced into evidence, wilful falsehoods would be criminal. (If included in a report in the United States, such declarations could be significant on the question of whether the report is "testimonial" hearsay that would trigger Con frontation Clause protections.)
• The report must state that "the witness will inform all parties and where appropriate the court in the event that his/her opinion changes on any material issues."
• "The witness must state any limitations to their experience and whether any particular issue, which is discussed in the statement (or on which they had been requested to discuss), falls outside their expertise."
• Consideration should be given to stating "[w]hether the witness tends to work for the prosecution, defence or both" amd "[w]hether the witness has been the subject of criticism and is aware of that criticism."
• Qualifications must be impartially listed, and "[t]he membership of an organisation which is obtained solely by applying for membership (and perhaps, payment of a fee) is not a qualification," and presenting such memberships as proof of expertise "is, at the least, irrelevant and may be misleading."
• "Where the witness is aware that reputable experts in the field would hold a range of opinions on the issue under consideration, the report must set out what that range is and justify why the witness’s opinion falls at a particular point within that range."
• The report should delineate "[a]ny results obtained which would undermine the opinion expressed"; [a]ny work, or other information, the witness is aware of which would undermine the opinion"; "[a]ny limitations to the analytical approach adopted"; and "[t]he uncertainty of measurement associated with the methods employed and the manner in which this has been addressed."

The document also advises experts "to avoid the term 'consistent'" because it "has been criticised by the Courts. It can sound significant but, in reality, mean little." On the other hand, "'not consistent' is usually clear and does not give rise to the same issues."

The guidance on "statistics" asks the expert to keep "detailed consideration" of "complex statistical analysis" out of the report but to make it available some other way. Moreover, it seems to place all "Bayesian inference" into this category! In full, the guidance is that

The Courts have, on a number of occasions, expressed concern about the evidence of complex statistical analysis (e.g. Bayesian inference) being discussed before the jury.
It is therefore advisable to avoid incorporating detailed consideration of such analysis in reports. The statement should set out the model employed and the conclusions drawn.
The details of the analysis should be available for disclosure.

This is a matter that the Regulator should reconsider in the next revision of the guidance -- along with the suggestion that "reference to statistical significance" is an "appropriate term" for explaining "how safe or unsafe" is "an inference from any findings." The phrase "statistical significance" has not fared well in recent policy pronouncements from statisticians.