Law commission: Expert Evidence

1. Law commission: Expert Evidence UEA Climatic Research Unit. Accusations of data manipulation. House of Commons Science & Technology Committee: ‘no intention to deceive’. Independent Review by Lord Oxburgh: “We cannot help remarking that it is very surprising that research in an area that depends so heavily on statistical methods has not been carried out in close collaboration with professional statisticians.”

2. Law Commission: Expert Evidence • The problem of ‘messy data’ • Measurements from individual weather stations simple; BUT • Some countries have many stations, others very few, and large areas of earth none. • This can lead to over-simplification, and dangerously misleading generalisation: eg Intergov. Panel on Climate Change: • Neglected discrepancy between direct and ‘proxy’ measurement such as tree ring data.

3. Law Commission: Expert Evidence • Paper commissioned from Prof David Hand: • Common sources of unreliability • Statistics commonly match data to theories: possible sources of error must be clear. • E.g. false positive rate; percent & proportion. • Theories must not predict too wide a range of possible outcomes. • Any ‘missing’ or ‘imperfect’ data must be accounted for. • Likewise possible sources of bias.

4. Law Commission: Expert • Distinguish: Subjective honesty, subjective-objective fairness, objective reliability. • Reliable enough for…..? • Distinguish: Scholarly speculation; civil litigation; criminal litigation. • Possible failure of honesty or fairness: Sally Clark (No.2) 2003. Prosecution expert fails to disclose test result for one of two infants. • Another expert in Clark faced ‘messy data’ problem: Cot death can be affected by environmental/genetic factors.

5. Law Commission: Expert Evidence • Clark: 2nd expert faced ‘fairness’ problems: data giving 1 in 73 mil chance of two SIDS cases in a family based on data that had warning of other possible influential factors. • Cannings (2004). Reliability fit for purpose? ‘Dogma’ that 2 or more unexplained infant deaths non-accidental. • Harris (2005) Reliability fit for purpose? Non-accidental head injury inferred from particular triad of intra-cranial injuries.

6. Law Commission: Expert Evidence • Lessons so far: • 1. Accept that a great deal of expertise make assumptions about matters outside its field. • 2. Do not conceal ‘inconvenient’ data! • 3. Be alert to purposes for which data may/not prove reliable. What is fine for scholarly speculation is a long way from what can pass muster as only or key evidence in the prosecution’s case. • 4. Cannings/Harris: support evidence only?

7. Law Commission: expert evidence Our aim is to reform the basis on which expert evidence is admissible. Expert evidence should only be admissible if the trial judge is persuaded that it is sufficiently reliable The judge should be assisted by guidelines and (if need be) a court expert

8. Law Commission: expert evidence • What is the present law? Bonython (1984): • Is the subject-matter of the opinion part of, “a body of knowledge or experience which is sufficiently organised or recognised to be accepted as a reliable body of knowledge or experience”, such that a special knowledge of it will make the witnesses opinion helpful? • In Luttrell [2004], the CA rejected the view that, to be admissible, there is a preliminary requirement that expert evidence involve a methodology that can be tested in cross-e.

9. Law Commission: expert evidence • There are problems of over and under-inclusiveness with the Bonython test. • Over inclusiveness: Cannings (2004), cot death; Harris (2005), shaken baby syndrome. • Under-inclusiveness: Some expert evidence that does not meet the Bonython criteria may nonetheless be perfectly reliable: • See Gilfoyle (no.2) (2001)). See, by contrast Robb (1991); Harris (2005).

10. Law Commission: expert evidence • Voice identification based solely on auditory comparison • Handwriting comparisons • Diagnoses of battered womens’ syndrome • Repression theory of sex abuse memory • ‘Gait’ comparison • Unreliable evidence: Dallagher (2002) • Problem of experience-based expertise

11. Law Commission: Expert Evidence • CPS guidelines for LCN DNA evidence: • Establish forensic scientist’s qualifications. • Check procedures in lab to avoid contamination. Does lab have documented processes? • Does evidence involve composite results? • How were profile results interpreted? • Were there variations or lack of reducibility in results?

12. Law Commission: Expert Evidence • HC Science and Technology Committee: • “An objective, clearly defined test to establish whether a theory or technique is sufficiently robust…to merit admission…[is] highly attractive” (2004-5). • Rule 702 of the Federal rules of Evidence, “If scientific…or other specialised knowledge will assist the trier of fact…a witness qualified by knowledge, skill, experience, training or education, may testify thereto..”

13. Law Commission: Expert Evidence • Daubert v Merrell Dow (1993): • 1. Ordinarily a key question is whether the theory or technique can be/has been tested. • 2. Has the theory or technique been subjected to peer review/publication? • 3. With particular techniques, the Ct should consider the known or potential error rate, and any standards for monitoring this. • 4. Widespread acceptance is important; techniques with minimal support should be viewed sceptically.

14. Law Commission: expert evidence • Our provisionally proposed solution, following Daubert. • 1. A ‘gate-keeping’ role for the trial judge. • 2. This involves a discretion to exclude otherwise relevant evidence, on grounds of unreliability. • 3. Discretion to be informed by guidelines on reliability. • 4. In difficult cases, judge to have power to call on an independent assessor.

15. Law Commission: expert evidence • General: expert opinion admissible only if the court deems it sufficiently reliable.* • Question of law: evidence predicated on sound principles, techniques, assumptions. • Question of fact: these principles etc have been properly applied in the case. • Question of fact: the evidence is supported by those principles etc as applied to the facts of the case. • Party relying on evidence must prove.*

16. Law Commission: expert evidence • Responses: over 80 individuals and organisations responded, mainly to support. • A selection of observations for improvement or change: • “Need for a warning to the jury that expert evidence can be wrong” (a solicitor). • In child death/injury cases, expert should come from separate health authority (campaigner).

17. Law Commission: expert evidence • Responses (cont.): • “Need to add to criteria: (a) attention to possible variations in the meaning of the opinion or its wording, (b) attention to whether expert’s confidence is accurately expressed, (c) does opinion addresses other explanations” (academic specialist). • Proposals should be extended to civil proceedings (several consultees).

18. Law Commission: expert evidence • Responses (cont.): • Experts must be properly prepared, and produce a written submission supporting methodology (specialist organisation). • There should be specialist working parties looking at science disciplines (like the one for forensic science) who could issue codes of practice (scholar). • Needs to be an inquisitorial stage where judge, experts and parties appraise evidence (senior judge).

19. Law Commission: expert evidence • Responses (cont.): • ‘Orthodoxy’ should be shown to be reliable and trustworthy before being admitted (campaigner). • Proposals should apply to expert assessments that an offender is ‘dangerous’, at the sentencing stage (lawyers’ organisation).

20. Law Commission: expert evidence • What are we now considering (A)? • 1. Court focus in testing admissibility should not just be on reliability, but also competence, impartiality, strength of opinion, necessity of the evidence for jury. • 2. Judge to follow a single set of generic guidelines, not divided between scientific and non-scientific expertise. • 3. Judge to rule of the scope of an expert’s area of expertise at the start.

21. Law Commission: expert evidence • What are we now considering (B)? • Trial judge to be allowed (i) to call informal hearing with parties/experts to discover precise extent of disagreement, and (ii) to make an order enabling the creation of a single document for the jury on outcome. • Defence will not have to go through hoops simply to rebut prosecution case, but they will if their case hinges on a ‘new theory’. • Judicial duty to consider a warning in some cases that expert opinion can be wrong.

22. Law Commission: expert evidence • Specific consideration for experts: • 1. They must be prepared to defend their methodology, not just their evidence. A role for professional bodies in producing guidelines? • 2. Such methodological material should be disclosed to the other side. • 3. Over-riding duty is to the court. So, if called to give evidence of probability of an event, assuming P’s case is true, they should be ready to do the same, if D’s case is true.