Expert Evidence: essays

There is no systematic deterioration in the ability of law to make sound judgments in criminal cases where scientific opinion evidence has important bearing on matters, even if doubt on its integrity has been cast over recent egregious errors. There are limitations on the capacity of science to depict the absolute truth and its conclusions always must be regarded as provisional. Law is not always aware of this. Science is not a privileged source of knowledge. It is socially constructed. Empirical studies attest high precision and objectivity in their findings but the design of studies affects the reliability of conclusions. Gatekeeper functions and rules of evidence would diminish pragmatism, flexibility and judicial discretion in court, notwithstanding that it would protect the jury from misleading evidence in some cases.[1]

Understanding of legal concepts as to expert evidence

Expert evidence is generally inadmissible on the issue of a witness’s credibility. In Re S (a child) (adoption: psychological evidence),[2] an appeal against a care order, the judge at first instance had relied on the results of a personality questionnaire, including a ‘Lie-Scale’ measuring the mother’s willingness to distort her responses in order to create a good impression. Allowing the appeal, it was held that the results of personality or psychometric tests should only rarely have any place in such cases because it is for judges to decide questions of credibility.[3]

Assess the current legal position and law commission’s proposal regarding expert evidence

The Law Commission’s central proposal was that there should be a new reliability-based admissibility test for expert opinion evidence which would need to be applied in relation to most expert opinion evidence tendered for admission in criminal proceedings. We proposed that there should be a rule along the following lines:

(1) The opinion evidence of an expert witness is admissible only if the court is satisfied that it is sufficiently reliable to be admitted.

(2) The opinion evidence of an expert witness is sufficiently reliable to be admitted if:–

(a) the evidence is predicated on sound principles, techniques and assumptions;

(b) those principles, techniques and assumptions have been properly applied to the facts of the case; and

(c) the evidence is supported by [that is, logically in keeping with] those principles, techniques and assumptions as applied to the facts of the case.[4]

The proposed test by Law Commission is a three-stage, with the evidence having to pass all three stages to be admitted. The first stage, which relates to the basis of the expert’s approach, tests whether the expert evidence is based on sound hypothesis, methodology and assumptions. This is done by addressing several criteria which are already familiar from Daubert, the most important of which are: testing (including adequacy of databases), error rates, relevant specialised literature, and impartiality of expert. The second stage relates to application, and tests whether the expert has applied the ideas correctly to arrive at their conclusions (and not for example made mistakes in calculations etc.). The last stage relates to reasoning, and tests whether the expert’s conclusions follow logically from their method (and, presumably, results).

In addition, three other ideas are floated:

(1) to have the possibility of an independent assessor appointed to help the judge evaluate admissibility in scientifically difficult cases;

(2) to have means of educating the relevant legal professionals in how to assess the scientific viability of expert evidence; and

(3) accreditation of experts.[5]

Critically evaluate as to whether the current legal position and law commission’s proposal is satisfactory or not

The current legal position, with respect to the second Bonython[6] requirement, is that, for expert evidence to be admissible in England and Wales, it must be “sufficiently well-established to pass the ordinary tests of relevance and reliability”. That is to say, the expert witness’s evidence must be sufficiently reliable to be fit for a jury to consider.

In Luttrell[7] the Court of Appeal expressly rejected the proposition that there is a preliminary requirement, for expert evidence to be admissible, that “the methods used are sufficiently explained to be tested in cross-examination and so to be verifiable or falsifiable”. It was accepted, however, that the trial judge could properly consider methodology when determining whether to exclude admissible prosecution expert evidence under section 78(1) of the Police and Criminal Evidence Act 1984; and the Court confirmed that an expert’s evidence could be ruled inadmissible on the ground that its “probative force is too slight to influence a decision”.[8]

Two other potential influences on jurors’ responses to the expert evidence were examined:

Oral vs Multimedia Evidence: Individuals have preferences for the way in which they gather and process information. If learning style and presentation mode do not match, learning may suffer. In this study, the DNA tutorial was presented orally or via multimedia to examine the influence of style on DNA knowledge.

Neutral vs Partisan Experts: The qualifications of the expert and the content of the testimony were held constant while the party introducing the expert was varied. For one half of the mock-jurors, the expert was court-appointed and introduced by the trial judge; for the other mock-jurors, partisan expert evidence was led by the Crown prosecutor.[9]

Expert opinion evidence

The opinion evidence of an expert is only admissible on a matter calling for expertise. The field of expertise is large and ever-expanding. It embraces subjects as diverse as accident investigation and driver behaviour,[10] the age of a person,[11] ballistics, battered women’s syndrome,[12] blood tests, breath tests, blood-alcohol levels and back-calculations thereof,[13] ear-print identification,[14] facial mapping[15] or facial identification by video superimposition,[16] fingerprint identification,[17] voice identification,[18] DNA or genetic fingerprinting,[19] indented  impressions left on one document as a result of writing on another, insanity, lip reading,[20] ‘shaken baby syndrome’,[21] Sudden Infant Death Syndrome (SIDS),[22] terrorism,[23] the genuineness of works of art, and the state of public opinion. Frequently recurring examples of matters upon which expert evidence is admissible include medical, scientific, architectural, engineering, and technological issues and questions relating to standards of professional competence, market values, customary terms of contracts, and the existence of professional and trade practices.

Handwriting may be proved either by a non-expert familiar with the handwriting in question or by a qualified expert, but an expert should be called in criminal cases tried by jury when, pursuant to section 8 of the Criminal Procedure Act 1865, disputed handwriting is compared with a specimen sample of handwriting proved to the satisfaction of the court to be genuine. Expert opinion is admissible on questions of a literary or artistic nature, for example in relation to the defence of ‘public good’ under section 4 of the Obscene Publications Act 1959.[24]

The law already provides sufficient safeguards as to the admissibility and evaluation of expert evidence in criminal proceedings. However, a significant risk will remain that the reliability of much expert opinion evidence will evade rigorous scrutiny. Further any problems that do exist are unlikely to be solved by the implementation of the Law Commissions proposals.

References

1. Cedric C. Gilson,  The Admissibility of Expert Evidence in Criminal Proceedings in Englandand Wales, The Law Commission Consultation Paper No 190, <http://www.academia.edu/195328/The_Admissibility_of_Expert_Evidence_in_Criminal_Proceedings_in_England_and_Wales > accessed on 2^nd August 2013.
2. G v DPP [1997] 2 All ER 755 at 759–60, CA.
3. Gumbley v Cunningham [1989] 1 All ER 5, HL.
   1. Jane Goodman-Delahunty and Lindsay Hewson, Improving Jury Understanding and Use of DNA Expert Evidence,  Report to the Criminology Research Council (2009), <http://www.criminologyresearchcouncil.gov.au/reports/05-0708.pdf> accessed on 3^rd April 2013.
   2. Opinion evidence, pp. 527-8, <http://fds.oup.com/www.oup.com/pdf/13/9780199698325.pdf> accessed on 2^nd April 2013.
   3. Phil Rose, Response to England and Wales Law Commission Consultation Paper 190:  The Admissibility of Expert Evidence in Criminal Proceedings in England and Wales:  A New Approach to the Determination of Evidentiary Reliability, <http://rose-morrison.forensic-voice-comparison.net/documents/Rose (2009) Response to Law Commission of England and Wales consultation paper.pdf > accessed on 2^nd April 2013.
   4. R v Ahmed [2011] EWCA Crim 184.
   5. R v Cannings [2004] 1 WLR 2607, CA, Ch 8.
   6. R v Clarke [1995] 2 Cr App R 425, CA.
   7. R v Dallagher [2003] 1 Cr App R 195, C; R v Kempster (No 2) [2008] 2 Cr App R 256, CA.
   8. R v Dudley [2004] All ER (D) 374 (Nov).
      1. R v Gordon [1995] 1 Cr App R 290, 293–4, CA.
      2. R v Henderson [2010] 2 Cr App R 185, CA.
         1. R v Hobson [1998] 1 Cr App R 31, CA.
         2. R v Luttrell [2004] 2 Cr App R 520, CA.
            1. R v Robb (1991) 93 Cr App R 161, CA.
            2. R v Robinson [1994] 3 All ER 346, CA
               1. R v Smith [2011] 2 Cr App R 174, CA.
               2. R v Stockwell (1993) 97 Cr App R 260, CA
               3. R (I) v Secretary of State for the Home Department [2005] EWHC 1025
               4. Re [2006] EWHC 1189 (Fam).
               5. Roberts, A. Drawing on expertise: legal decision-making and the reception of expert evidence CRIM LR (2008) 443
                  1. The Law Commission Consultation Paper No 190,  The Admissibility of Expert Evidence in Criminal Proceedings in England and Wales,  A New Approach to the Determination of Evidentiary Reliability,  A Consultation Paper, <http://lawcommission.justice.gov.uk/docs/cp190_Expert_Evidence_Consultation.pdf> accessed on 1^st April 2013.
                  2. The Law Commission  (LAW COM No 325),  Expert Evidence in Criminal  Proceedings in England and  Wales,  Presented to Parliament pursuant to section 3(2) of the Law  Commissions Act 1965, <http://lawcommission.justice.gov.uk/docs/lc325_Expert_Evidence_Report.pdf> accessed on 2^nd April 2013.
                  3. The Queen v. Bonython (1984) 38 SASR 45.