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Max Planck Encyclopedia of Comparative Constitutional Law [MPECCoL]

Role of Experts in Judicial Proceedings

Dana Phillips

From: Oxford Constitutions (http://oxcon.ouplaw.com). (c) Oxford University Press, 2015. All Rights Reserved.date: 24 November 2020

Effectiveness — Administrative law — Administrative procedures

Published under the direction of the Max Planck Foundation for International Peace and the Rule of Law.
General Editors: Rainer Grote, Frauke Lachenmann, Rüdiger Wolfrum.

A.  Definition

1.  Core Meaning

1.  In the context of judicial proceedings, an expert is someone who has specialized skills, knowledge, or experience, often of a scientific or technical nature, and is thereby called upon to assist the court.

2.  The Anglo-American common law tradition and the Continental civil law tradition have established distinct roles for experts in judicial proceedings. In the common law tradition, experts testify as witnesses, and are usually appointed and paid for by the parties. Expert witnesses are exempted from the traditional rule barring witnesses from giving opinion evidence. While witnesses are generally restricted to testifying about their direct observations, expert witnesses may offer opinions based on their observations or other established facts (Hand 43–45).

3.  In the civil law tradition, courts typically appoint experts as assistants or auxiliaries of the court. Such experts are distinct from witnesses, and may be seen to exercise quasi-public authority, for instance in France and Austria (Cuniberti 8; Verkerk 168–170). In England, ‘assessors’—used primarily in admiralty and patents cases—play a comparable role (Dwyer 324–331).

4.  In both traditions, parties may also hire private experts to guide them in handling a case. Such experts are not authorized by the court and do not produce ‘legal’ expert reports (Nuée 11).

5.  As specialized knowledge accumulates, and litigation becomes more complex, experts play an increasingly important role in judicial proceedings around the world (Farrow and Watson 156). The evolving role of experts affects widespread constitutional principles such as the right to a fair hearing and independence of the judiciary. In many jurisdictions, experts have also become vital to fact-finding in constitutional cases.

B.  Evolution of the Role of Experts

1.  Common Law

6.  Before the advent of the modern adversarial system in eighteenth century England, courts received expert assistance via special juries and court advisors (Golan 6). Both practices date back at least to the fourteenth century, prior to the summoning of witnesses (Hand 41–42; 44).

7.  Special juries were composed of people whose backgrounds made them especially suited to decide the facts of a case. For instance, trade disputes in London during the fourteenth century often relied upon juries of tradesmen (Hand 41). The use of special juries today would raise a constitutional difficulty related to fair hearing rights; where one party belongs to the same group of specialists as the jury, the jury may be, or appear to be, biased (Dwyer 38–39).

8.  In addition to special juries, judges historically sought assistance from experts such as physicians and grammarians as court advisors (Hand 43). Experts also appeared as witnesses, especially from the Tudor period onwards (Golan 21). However, they were not distinguished from lay witnesses, or otherwise accorded the expert status of special juries and court advisors (Golan 22).

9.  In eighteenth century England, lawyers began to take greater control of conducting cases and presenting evidence, establishing the adversarial, party-controlled model of litigation that remains prevalent in the common law world today. In the process, court-controlled special juries and court advisors gradually gave way to partisan expert witnesses (Hand 40). The 1782 opinion of Lord Mansfield in Folkes v Chadd (UK) is often cited as establishing the modern rules governing expert evidence (Golan 6). There, Lord Mansfield found that ‘men of science’ should be allowed to give opinions based on established facts, regardless of the type of science (Folkes v Chadd (UK) 590; Golan 45). This finding effectively created an exception to the rule barring opinion evidence.

10.  In recent decades, civil procedure has undergone significant reforms across the common law world, spurring many changes to the rules governing experts. In the United Kingdom (‘UK’), Lord Woolf’s 1996 Access to Justice Report (‘Woolf Report’) led to the enactment of the Civil Procedure Rules (‘CivPR’) of 1998 and accompanying Practice Directions (‘PD’), which incorporate many of the report’s recommendations to reduce the costs of expert evidence. Similar reform efforts in Australia and Canada have led to the establishment of new rules governing expert evidence at the federal and state/provincial levels.

2.  Civil Law

11.  Unlike the common law, the civil law systems of Continental Europe were heavily influenced by the Romano-Canonical law revived in northern Italy during the Middle Ages. In this tradition, experts were not recognized as ‘true’ means of proof, but nevertheless acted as assistants to the judge (Engelmann and Millar (eds) 361–362). They were, for instance, commonly used in land boundary disputes (Engelmann and Millar (eds) 362).

12.  Expert forensic evidence was already a part of Continental proceedings in the thirteenth century (Havard 31). Measures regulating the qualifications of experts were implemented early on, with expert registers being established in Italy and France (Havard 31; Engelmann and Millar (eds) 719). Expert evidence was given mainly in the form of written reports (Havard 36).

13.  In France, the Ordinance of 1667 was the first statute to recognize expert reports as a true means of proof in civil cases (Engelmann and Millar (eds) 719). The Ordinance of 1670 regulated the use of expert reports in criminal cases. The use of expert reports to help the judge inspect material evidence of a crime is an old custom in France (Esmein 622).

14.  Most civil law countries now list experts as a means of evidence (Verkerk 170).

3.  Islamic Law

15.  In classical Islamic courts, experts were regularly summoned to assist with cases, a practice justified by precedent in religious texts (Shaham 27–29). Muslim jurists viewed expert opinion as falling somewhere between two traditional forms of evidence: 1) transmission (paradigmatically, of religious traditions); and 2) witness testimony (Shaham 53–54). However, experts were more closely associated with the latter (Shaham 54). Depending on the case, experts were summoned by Shari’a judges (qadis) as advisers, or called as partisan witnesses (Shaham 58–59).

16.  The role of experts in modern Islamic nations has been strongly influenced by European legal traditions. In Egypt and other states that have adopted elements of civil law, experts are no longer treated as witnesses (Shaham 107).

C.  Comparative Role of Experts

1.  General Constitutional Concerns

17.  As a framework for comparative analysis, it is useful to begin by outlining the most pervasive concerns regarding the role of experts in the common law and civil law traditions from a constitutional perspective. These concerns relate primarily to constitutionally enshrined fair hearing rights, and the related constitutional principle of judicial independence.

18.  Fair hearing rights ensure that the parties to a proceeding have the opportunity to make their case by presenting and responding to evidence, and that the decision maker is independent and impartial (see right to a fair hearing in civil law cases; right to a fair hearing in criminal law cases). Criminal defendants often benefit from special procedural guarantees under the banner of fair hearing rights, in order to protect the presumption of innocence and guard against wrongful convictions.

19.  As noted by the Supreme Court of Canada in the Beauregard case, the principle of judicial independence has both an individual and an institutional component (Beauregard v Canada (Can), para. 23). While the independence of the individual judge from any external influence has a long constitutional history, and is generally incorporated within the right to a fair hearing, judicial independence in the institutional sense is rooted in the evolving constitutional function of courts in modern democracies (Beauregard v Canada (Can), at paras 21–22). That is, to the extent that courts are charged with protecting the constitution, the judiciary must remain independent from the executive and legislative branches of government, as well as from other actors (Valois 233–235).

20.  The participation of experts in judicial proceedings can serve both to safeguard and to threaten fair hearing rights and judicial independence. On the one hand, the opportunity to have an expert appear before the court may be essential to the effective presentation of a party’s case, and thus to a fair hearing. The European Court of Human Rights (ECtHR) has noted that, according to Article 6 of the European Convention for the Protection of Human Rights and Fundamental Freedoms (1950) (‘ECHR’), which guarantees the right to a fair trial, parties must be afforded the opportunity to bring evidence necessary to the success of their claims (see Mantovanelli v France (Eur)). In Kosovo, a criminally accused person has a constitutional right to have an expert attend proceedings to clarify the evidence (Constitution of the Republic of Kosovo: 9 April 2008 (as Amended to 24 February 2016) Art. 31 (Kos)). Similarly, criminal defendants in Bolivia have a constitutional right to ‘request the presence and confront witnesses or experts’ (Constitution of the Republic of Bolivia: 2 February 1967 (as Amended to 8 August 2002) Art. 16 (Bol)). The participation of experts may also support the role of courts as effective guardians of the constitution, by ensuring that decisions about complex constitutional issues are properly informed.

21.  On the other hand, expert participation in judicial proceedings can sometimes allow one party to gain an unfair advantage over another, contrary to fair hearing rights, and can threaten the independence of judicial decision-making. There are at least three interrelated reasons for this: 1) expert bias; 2) the challenges of assessing expert opinion as a non-expert; and 3) the costs of expert participation in judicial proceedings. These issues arise in a somewhat different manner and with different consequences in the common law and civil law traditions.

(a)  Common Law

22.  In the common law tradition, critiques have long been raised about the biases that arise from partisan experts, and the distorting effects of the adversarial process on scientific knowledge (Anderson 22–30). There is empirical evidence to support the concern about bias in Israel and the United States (‘US’) (Perez 101; Verkerk 187).

23.  Some scholars argue that the adversarial system exposes genuine disagreements within the relevant field that would be difficult to uncover via a single expert (Golan 3–4). However, such arguments lose force when the parties are not equally equipped to engage in the adversarial process. For instance, criminal prosecutors tend to have far greater resources to gather and present expert evidence (and to challenge opposing experts) as compared to accused persons (Edmond and Roach 362–363). Moreover, many fields of forensic science are strongly linked to law enforcement institutions, making it difficult for criminal defendants to find critical experts (Edmond and Roach 363–364). The need to hire and respond to multiple experts has also inflated the costs of civil litigation and created barriers to justice for less wealthy litigants (see Woolf Report).

24.  Given the importance of experts to fact-finding in constitutional cases (see Part D), a lack of resources may prevent individuals from bringing important constitutional challenges, or tilt the weight of expert opinion in favour of the state in challenges that are brought, impeding robust judicial enforcement of constitutional rights.

25.  The above problems are exacerbated by the inherent difficulties that non-expert decision makers in any legal tradition face in properly evaluating expert knowledge (Perez 77). In the common law context, judges and juries may thus find themselves ill-equipped to assess competing expert opinions. As Learned Hand once noted: ‘[i]t is just because they are incompetent for such a task that the expert is necessary at all’ (Hand 54). In other words, the very rationale for the participation of experts in judicial proceedings is also a source of the trouble they create.

(b)  Civil Law

26.  While concerns about the role of experts in the common law tradition centre around partisanship, critiques of the civil law tradition often point to the problematic relationship between the expert and the judge. Given the challenges of competently assessing expert knowledge, the danger in the civil law context is that a judge may defer too readily to the opinion of a court-appointed expert. If so, it may be that the expert effectively usurps the judge’s role as decision maker, contrary to the constitutional principle of judicial independence (Verkerk 181).

27.  While there is less risk of expert bias arising from partisanship in the civil law tradition, the strong influence of court-appointed experts on judicial decision-making, and the quasi-judicial nature of the expert’s role as auxiliary of the court, heightens the consequences of any bias that may arise. The ECtHR has found that a lack of neutrality on the part of a court-appointed expert may violate the principle of equality of arms inherent in Article 6 of the ECHR (Sara Lind Eggertsdóttir v Iceland, para. 47). In Egypt, the independence of judicial experts is constitutionally protected (Constitution of the Arab Republic of Egypt: 18 January 2014, Art. 199 (Egypt)).

28.  Court-appointed experts also present the danger of collaboration; given that the judge who appoints the expert also controls his or her payment, the expert may be inclined to support the judge’s pre-existing view of the case (Nuée 14; Dwyer 193). This could affect the fair hearing rights of a party whom the judge is inclined to decide against.

29.  As in the common law context, the participation of party-appointed experts in civil law jurisdictions increases the risk of expert bias arising from partisanship, and heightens the potential constitutional impact of an imbalance in resources between the parties. The concern about unequal resources also arises where parties hire their own private experts to assist in challenging a court-appointed expert.

2.  General Role of Experts

30.  The evolving role of experts in the common law and civil law traditions is informed by the constitutional concerns described in the previous section. Some aspects of the expert’s role are common across legal traditions. For instance, in recognition of the threat of bias, it is widely affirmed that experts should be competent, independent, and impartial. It is also widely accepted that experts should only be called upon when needed to address matters beyond the understanding of the trier of fact—a limitation that controls the costs of expert evidence and preserves the authority of courts over the fact-finding process.

31.  Recent developments suggest some convergence even on traditional points of difference between common and civil law systems (Bamford 161). Given the distinct constitutional concerns that arise from each tradition, there is a growing consensus regarding the benefits of mixed models that allow a role for both the court and the parties in expert procedures (Verkerk 194).

32.  Recent procedural reforms have moved many common law countries closer to the civil law model by expanding the codification of rules governing experts, emphasizing the expert’s duty to the court, and creating provisions for court-appointed experts. The US, however, has resisted such reforms, and continues to strongly prefer party-appointed experts (Arnold and Soriano 2; Verkerk 193).

33.  Civil law jurisdictions such as Spain and China have moved closer to the common law model by enhancing the role of parties in appointing experts and challenging expert opinions (Nuée 10; Durney 29–30). Many civil law countries also recognize a role for party-appointed experts.

34.  While some countries, like the US and Austria, have held fast to their respective traditions, others, like the UK and China, have made significant strides towards a mixed model (Verkerk 193; Durney 29).

3.  Ethical Duties and Liabilities

35.  In a widely influential UK case known as The Ikarian Reefer, Justice Cresswell set out the duties of expert witnesses in civil cases (see National Justice Compania Naviera SA v Prudential Assurance Co Ltd (UK)). Notably, he affirmed that experts should provide objective and independent assistance to the court within the scope of their expertise, and should state the facts and assumptions on which their opinions are based. The duties set out in The Ikarian Reefer and expanded upon in subsequent case law have been enshrined in the UK’s CivPR (Part 35) and Criminal Procedure Rules (‘CrimPR’) (Part 19), and have been cited in jurisdictions around the world, including Canada, Australia, Scotland, Singapore, South Africa, Hong Kong, and the Bahamas (Anderson 208).

36.  Many common law jurisdictions have established expert codes of conduct within procedural rules. One function of these codes is to emphasize duties that already exist at common law, most notably, the expert’s overriding duty to the court (Bamford 164). In many jurisdictions, including the UK, Canada, Australia, and New Zealand, experts are required to formally acknowledge their codified duties. Unlike other common law jurisdictions, the US Federal Rules of Evidence (‘FRE’) are silent regarding the expert’s duty to the court, though rule 706 does stipulate that the court must inform a court-appointed expert of his or her duties.

37.  In civil law jurisdictions, the ethical duties of experts are often enshrined in procedural codes. Many countries have codified the impartiality requirement along with procedures for recusal where the requirement is not met (Verkerk 179). Given the expert’s role as auxiliary of the court, the expert’s duties in civil law countries often parallel those of the court. For example, in France and Germany an expert may be recused for the same reasons as a judge (Code de procédure civile, Art. 234 (Fr); Code of Civil Procedure 2005, including amendments up to 10 October 2013, Section 406 (Ger)).

38.  Experts are subject to civil and/or criminal liability in almost every country of the European Union (‘EU’), with the exception of Cyprus and Ireland (Nuée 18). In the UK, expert immunity from civil suit was abolished in the 2011 case of Jones v Kaney (Jones v Kaney (UK), para. 62). The immunity still exists in other common law jurisdictions such as Australia (Turner 16).

4.  Appointment and Qualification

(a)  Appointment

39.  One of the central distinctions between the role of experts in common and civil law systems is the method of appointment. Common law experts are traditionally appointed and paid for by the parties, raising concerns about bias arising from partisanship, and the parties’ respective capacities to make effective use of experts. In civil law systems, the court typically appoints an expert and controls his or her fees, raising concerns about the independence of the judge from the expert. However, many jurisdictions now include both methods of appointment.

40.  In the wake of civil procedure reforms, the rules in many common law jurisdictions now allow for experts who are jointly selected by the parties, or, where the parties cannot agree, appointed by the court (eg CivPR, Part 35.7 (UK)). Single joint experts have proven popular in the UK (Further Findings, Section 4.24). However, courts in many jurisdictions remain reluctant to appoint experts without party agreement (eg Bamford 169; Jurs 1354–1355 (US)), despite the urging of scholars and even some judges (Perez 93, 108; Binnie 191). This is due in part to the strong tradition of party autonomy over the presentation of evidence in the common law (Bamford 169; Verkerk 195–6).

41.  Still, court-appointed experts have taken root in some areas of the common law world. For example, in response to strong criticism of partisan experts in tort cases, Israel established a regime for car accident cases that allows only court-appointed experts (Perez 91–93). Israeli courts also sometimes use court-appointed experts to help assess competing partisan experts (Perez 94), a practice that also exists in the US (Cecil and Willging 20) and in Mexico (a civil law country) (Código Federal De Procedimientos Civiles, Arts. 146 and 152 (Mex)).

42.  It is not uncommon for civil law judges to appoint experts ex officio. Nevertheless, experts are often appointed at the suggestion of the parties, and parties in some countries (eg Austria, Netherlands) have a right to be heard on this (Verkerk 170–171). Recent amendments to the civil procedure rules in China establish a preference for experts to be jointly selected by the parties, as in the UK (Durney 29).

43.  In several civil law countries, the prosecution in a criminal case can summon experts to assist with the investigation or pre-trial proceedings (see Matrix; Newcombe 312; Weigand 211). The prosecution may thereby influence the court’s selection of the trial expert, raising concerns about expert bias in favour of the state. For instance, although the power to appoint experts lies with the court in Germany, in practice the court will often retain the expert summoned by the prosecutor (Weigand 211).

44.  Court appointments are generally limited to a single expert, with the option to appoint more if needed. In Columbia, the court will appoint two independent experts upon request of the parties. If the expert reports contradict each other, the court will appoint a third expert as referee (Abbud et al. 16).

45.  In many civil law jurisdictions, party-appointed experts are allowed to play a role in the proceedings, though the weight accorded to their opinions varies. In Germany, partisan expert reports may be submitted to the court, but do not count as evidence and hold little weight, though under recent reforms they can no longer be disregarded without explanation (Timmerbeil 177–179). In the Netherlands, on the other hand, party-appointed experts can be heard as witnesses (Verkerk 189). Spain has moved even further towards the common law model by limiting the judge’s power to appoint experts in favour of party-appointed experts in most cases (Ley No. 1/2000 de 7 enero, de enjuiciamiento civil, exposición de motivos XI (Spain)).

(b)  Qualification

46.  The strong deference shown to court-appointed experts heightens the importance of selection procedures and quality assurance measures (Perez 109). Given the ubiquity of court-appointed experts in civil law systems, many such countries, including Germany, Austria, France, Italy, Japan, Egypt, and Morocco keep registers of pre-vetted experts (Perez 110; Verkerk 172; Shaham 110). The vetting process differs in each country; it may be overseen by courts, administrative bodies, professional associations, or by a centralized agency (Perez 110). In Germany, for instance, candidates must prove their qualifications before commissions established by regional chambers (Deshayes 10). In Japan, the Supreme Court maintains a registry of ‘expert commissioners’ (Jurs 1399). In other countries, such as the Netherlands, courts keep informal lists of experts as a reference (Verkerk 172). Enrolment as a registered expert may be permanent or subject to renewal every few years (Nuée 16). While registers offer some assurance of quality, most jurisdictions still allow courts to appoint non-registered experts where necessary (Nuée 6).

47.  In addition to keeping an expert registry, Egypt has established a system of state-employed experts (Shaham 109–111).

48.  The risk of expert bias increases where court-appointed experts are selected on the basis of established social connections or ideological affinities, rather than professional reputation (Perez 103 and 110). Such dangers are exacerbated in common law countries lacking well-established and transparent vetting procedures for court-appointed experts, such as Israel (Perez 103). However, even in countries with more transparent procedures, a judge may develop a preference for a particular expert. There is empirical evidence of magistrates repeatedly pairing up with the same medical experts in France, for example (Dwyer 193). A judge may be more likely to defer to an expert who is familiar in this way. On the other hand, the judge may have selected the expert so as to confirm his or her own views (Dwyer 193).

49.  In the UK, the Academy of Experts and the Expert Witness Institute provide expert training. The Academy of Experts also accredits and disciplines experts. However, many experts who appear in courts are not members of these non-governmental organizations (Anderson 217–218). The US has similar organizations, as well as expert lists published by some bar associations (Verkerk 185).

50.  At common law, the party seeking to bring expert evidence has the burden to demonstrate that the expert is properly qualified. The judge makes the ultimate determination (Turner 10).

5.  Mission and Reporting Procedures

(a)  Mission

51.  While courts generally hold ultimate control over the participation of experts in judicial proceedings, courts in civil law systems manage the process much more actively. The degree of control exercised varies. For example, in Germany, the judge poses highly specific technical questions to the expert, significantly narrowing the scope of the expert’s mission, and minimizing his or her influence over the outcome. In contrast, experts in France are given more general instructions, and have greater autonomy in the preparation of their reports (Deshayes 14–16).

52.  Common law jurisdictions leave control of the expert’s mission largely in the hands of the parties. Nevertheless, some jurisdictions have taken steps towards increased judicial control, for instance via rules that require the parties to seek leave from the court to call expert evidence (Bamford 170; CivPR, Part 35.4(1) (UK)). Common law judges play a more active role in controlling the admissibility of expert evidence.

53.  Historically, in order to ensure that they did not usurp the role of the trier of fact, common law experts were barred from giving opinions on the ultimate issue(s) in a case. This rule has now been abolished or weakened in many jurisdictions, including the UK, the US, and Canada (Dwyer 274–279; US FRE 704; R v Mohan, para. 25 (Can)). However, the concerns driving the rule remain (R v Mohan, para. 25 (Can)).

(b)  Reporting

54.  In civil law jurisdictions, court-appointed experts primarily produce written reports. They may also be called to testify orally about their report if requested by the court or the parties. In some countries, such as Russia and Japan, experts can even be involved in witness examination (Newcombe 313; Jurs 1400–1401).

55.  The common law traditionally places more emphasis on experts’ oral testimony and cross-examination in court. However, common law jurisdictions also require experts to produce written reports for disclosure. In many jurisdictions, expert codes of conduct now set out detailed requirements for such reports. Typically, reports must include the expert’s qualifications, issues addressed, facts and assumptions relied upon, materials used, investigations conducted, and any necessary caveats. In Queensland, experts must also justify their opinion within a range of possible views, and outline additional facts that could help them to reach a more reliable conclusion (Uniform Civil Procedure Rules, Section 428). Some jurisdictions (eg South Australia) have established additional disclosure requirements, leading parties to hire ‘shadow’ experts who can offer advice without participating in the proceedings (Bamford 166–167).

(c)  Party Challenges

56.  According to the ECtHR, the adversarial principle protected under Article 6 of the ECHR gives parties the right to inspect and comment on all evidence and observations filed with a view to influencing the court’s decision (Mantovanelli v France, para. 33 (Eur)).

57.  Many civil law jurisdictions allow the parties to question court-appointed experts in court, though the approach taken is far from the aggressive cross-examinations prevalent in common law jurisdictions (Verkerk 186). The German Constitutional Court has found a violation of fair hearing rights in several cases where a court dismissed a party’s request to question an expert at an oral hearing (1 BvR 2485/06 (Ger); 1 BvR 909/94 (Ger)).

58.  In France, on the other hand, the main chance for the parties to challenge expert evidence is prior to the submission of the expert’s written report (Jeuland 202–203). If an expert report is likely to have a strong influence on the court, Article 6 of the ECHR may require that parties have a chance to participate in the expert’s investigation prior to the report’s submission (Mantovanelli v France, para. 36 (Eur)).

59.  There is some concern that the role of assessors in UK admiralty cases violates Article 6 of the ECHR (Dwyer 325). Prior to the introduction of the CivPR, judges consulted with nautical assessors in private following the conclusion of a hearing, making it impossible for the parties to effectively challenge the assessor’s opinion (Dwyer 324). Under CivPR rule 35.15 (3), the court may ask the assessor to produce a pre-trial report, however the parties are still not allowed to cross-examine the assessor (Dwyer 325).

6.  Admissibility and Weight

(a)  Admissibility

60.  Unlike in the civil law tradition, common law jurisdictions have developed complex rules to regulate the admissibility of evidence, including expert evidence. In recent years, much of the jurisprudence has focused on the issue of reliability. The concern about reliability has been driven by the proliferation of ‘junk science’ in the courts and by resulting miscarriages of justice, including wrongful convictions (Anderson 156–61, 193–205; see Goudge Report). In the US, the proliferation of mass tort litigation hinging on expert evidence has had a strong influence on the development of stricter reliability standards (Edmond and Roach 344, 350).

61.  In the leading US case of Daubert v Merrell Down Pharmaceuticals, the Supreme Court highlighted the court’s role in ‘gatekeeping’ against the admission of unreliable expert evidence. The Court interpreted FRE 702 to require that scientific evidence be reliable, and offered a flexible list of factors for assessing reliability. In Kumho Tire CO v Carmichael (US), the Supreme Court clarified that the reliability requirement also applies to non-scientific expert knowledge. The new case law was eventually codified via an amendment to rule 702. While its application has been inconsistent across state courts (Anderson 176) and has had minimal effects on American criminal proceedings (Edmond and Roach 354), it has been influential in other countries such as Canada, where courts have adopted a similar approach (R v J-LJ, paras 33–34). The UK has resisted calls to legislate a reliability standard for admissibility, preferring to consider reliability in weighing the evidence (Jurs 1376–1380). However, UK courts have established that evidence must be ‘sufficiently reliable’ to be admitted in the criminal context (CrimPR PD 19A.4, citing Dlugosz at para. 11 (UK)).

62.  In practice, reliability standards are sometimes applied unevenly to the expert evidence brought by different types of litigants due to resource imbalances between parties, as well as ideological and institutional pressures (Edmond and Roach 404). For instance, in the US, Daubert and its progeny were used primarily to further the trend of excluding plaintiff-side expert evidence in civil litigation against corporate defendants, at a time of corporate-driven tort law reform campaigns (Edmond and Roach 353–355). Expert evidence brought by the state in criminal cases, on the other hand, has been subject to far less scrutiny, with courts more inclined to exclude expert evidence from the accused than from the prosecution (Edmond and Roach 358; 363). Similar trends appear across the common law world (Edmond and Roach 398). The uneven application of reliability-based admissibility standards poses a threat to fair hearing rights and other constitutionally grounded principles, especially in the criminal context.

63.  In an effort to uphold fundamental values such as the presumption of innocence and the prevention of wrongful convictions, Edmond and Roach have argued for an asymmetrical approach that would place a higher burden on the state to demonstrate reliability when adducing expert evidence than on criminal defendants (Edmond and Roach 348). They have also advocated for recognition of a constitutional right not to be confronted with unreliable expert opinion evidence as an accused person (Edmond and Roach 388).

64.  In addition to reliability, a lack of impartiality may also render expert evidence inadmissible in Canada and England, whereas in Australia and the US, this goes to weight (Hunt and Neudorf 73–74).

(b)  Weight

65.  Courts generally are not bound by expert opinions. Nevertheless, such opinions can be highly influential, especially when derived from court-appointed experts, as is often the case in civil law systems. Party challenges to the methodology or findings of court-appointed experts tend to be ineffective (Verkerk 181). In one Israeli study, cross-examination of court-appointed experts was found to have no significant effect on the court’s tendency to adopt the expert’s conclusions (Perez 100). Studies in common law jurisdictions have revealed similar limitations on the effectiveness of cross-examination and other trial safeguards as means to screen expert evidence (Edmond and Roach 365). Such findings heighten the concern that experts pose a threat to judicial independence.

66.  A survey of representatives from EU Member States indicates that in several countries (eg Norway, Portugal), expert evidence is accorded more weight than other evidence in practice. The respondent from Greece noted that evidence given by public authorities or by the forensics laboratory of the police is accorded more weight than other evidence (see Matrix).

D.  Current Developments and Reforms

1.  Common Law Innovations

67.  Common law countries have undertaken procedural reforms to limit the costs of experts and to better ensure their impartiality. Broadly speaking, these include strengthening the duties of expert witnesses, ensuring more active court management of expert evidence, and providing for alternative expert selection procedures (Bamford 164).

68.  One innovation from Australia is the use of concurrent evidence, informally known as ‘hot tubbing’. In contrast to the traditional presentation of evidence by each party sequentially, experts from both sides are heard at the same time via a joint panel format. The experts answer questions from counsel, the judge, and other experts on the panel (Edmond 162–164). Proponent judges have argued that this format clarifies the evidence, decreases costs, and reduces the distorting effects of adversarialism on scientific opinion (Edmond 167–169). However, some scholarship suggests that the benefits may be exaggerated (Edmond). The use of concurrent evidence dates back to the 1970s in Australia, and has recently begun to spread (Edmond 166).

69.  Expert conferences, whereby experts meet in advance of trial to narrow the issues in dispute, offer another avenue to reduce costs and clarify the evidence (Arnold and Soriano 19–20). By requiring opposing experts to share information, expert conferences can mitigate resource imbalances between the parties (Dwyer 187), and thereby enhance trial fairness. Such conferences may be used in conjunction with concurrent evidence (Edmond 165).

70.  There have also been efforts to develop stronger professional standards for experts, especially in forensic science, which has been the subject of calls for reform from multiple jurisdictions (Perez 112; Du 71; Edmond and Roach 348).

2.  Cross-Border Litigation in the EU

71.  The handling of expert reports in cross-border litigation has become a significant issue in the EU. The principle of mutual recognition of judicial decisions does not apply to expert reports (Deshayes 8). Courts often reject foreign expert reports for lack of knowledge, or trust in, the expert system in the other Member State. This can lead to duplication in expert proceedings, raising problems of inconsistency and wasted resources (Cuniberti 19–20). There is now a push to harmonize the regulation of judicial experts across the EU to allow for the free circulation of experts and expert reports.

E.  Experts in Constitutional Cases

1.  Role of Experts in Constitutional Cases Generally

72.  Experts, especially from the social sciences, have come to play an important role in fact-finding in constitutional cases. In a broader sense, expertise also figures in other aspects of constitutional cases, such as in the monitoring and enforcement of structural injunctions (see Gillespie). However, for reasons of scope, this article focuses on the role of expert knowledge in the fact-finding process.

73.  In most contexts, fact-finding in judicial proceedings is directed towards the particulars of the case at hand. Where constitutional issues arise, however, the focus shifts to general, contextual facts that help the court to fulfil its law-making function. Davis originally identified this distinction as one between ‘adjudicative’ and ‘legislative’ facts (Davis 402). Faced with the need to address complex questions of legislative fact in constitutional cases, courts and parties have increasingly turned to experts for assistance.

2.  Civil Law: Specialized Constitutional Courts

74.  Unlike most common law countries, civil law countries often have specialized constitutional courts. Many such courts—notably those in Germany, Austria, Russia, and much of Eastern Europe—include provisions on the role of experts in their governing legislation. Typical are provisions allowing the court to appoint one or more experts (eg Act on the Constitutional Court (No. 182 of 1993): June 16 1993 (as Amended to 2004) Art. 50 (Czech)); allowing the court to frame the question(s) to be answered by the expert(s) (eg Federal Constitutional Law on the Constitutional Court of the Russian Federation: June 24 1994 (FCLCC) Art. 63 (Russ)); granting investigating powers to the expert(s) (eg Law of the Constitutional Court of the Republic of Lithuania: February 3 1997 (as Amended to November 19 2003) No I-67, Art. 37 (Lith)); and allowing the parties to question the expert(s) (eg Federal Constitutional Court Act: March 12 1951 (as Amended to July 12 2012) Art. 29 (Ger)). In Armenia and Russia, experts may also question the parties at the hearing (Law of the Republic of Armenia on the Constitutional Court: December 9 1997, Art. 47 (Arm); Russian FCLCC, Art. 62 (Russ)).

3.  Common Law: Canada and the US

75.  In common law jurisdictions like Canada and the US, where there are no specialized constitutional courts, the same evidentiary rules and procedures apply to constitutional cases as to other cases. However, there is a lack of clarity regarding the appropriate use of expertise to establish legislative facts in constitutional litigation (Young 637; Faigman xii). In particular, challenges arise in determining which matters ought to be treated as facts calling for expert opinion, and the appropriate manner of bringing such opinion into the fact-finding process.

(a)  Facts Calling for Expert Opinion

76.  The first challenge is to determine which contextual matters ought to be treated as facts calling for expert opinion, rather than being determined in the course of judicial reasoning. Requiring expert proof of legislative facts shifts authority from legal sources of knowledge to other, more empirically grounded disciplines. Suzanne Goldberg observes that deciding legislative issues on a factual basis may provide institutional license for courts to make progressive decisions that drive social change, by obfuscating controversial normative judgments under the guise of empirical facts (Goldberg 26).

77.  On the other hand, calls for expert opinion to support legislative facts in constitutional cases raise concerns about access to justice (Boyle and MacCrimmon 67). Many would-be rights-seekers lack the resources required to bring extensive expert opinion in support of a constitutional challenge, especially where such opinion must be formally introduced as evidence through an expert witness.

(b)  Manner of Entry

78.  A second challenge regarding which courts have offered scant guidance relates to the manner in which expertise should enter the fact-finding process. In addition to being presented through the testimony of expert witnesses, the work of experts is sometimes cited in legal briefs, and independently researched by judges (Larsen 1759).

79.  Louis Brandeis is credited for the first submission of a legal brief consisting largely of social science data—what came to be known as a Brandeis brief—in the 1908 US case of Muller v Oregon (Larsen 1770). Brandeis represented the state in Muller, however the Brandeis brief gained popularity as a way for non-party amici curiae (‘friends of the court’) to bring research data to the attention of appellate courts.

80.  Originally, an amicus curiae was a neutral lawyer present in the courtroom who assisted the judge by raising relevant points of law (Larsen 1765). However, as constitutional litigation began to shape American social policy in the mid-twentieth century, amicus briefs came to be used by private interest groups as a tool for political advocacy, especially at the Supreme Court of the United States. This gave rise to concerns about the growth of partisan, litigation-driven legal research (Fisher and Harriger 9). The use and influence of amicus briefs as a source of off-the-record factual expertise in the Supreme Court has since increased significantly (Larsen 1768). Critics such as Larsen have noted that amicus briefs are not effectively tested through the adversarial process, and have raised doubts about their reliability (Larsen 1763–4). On the other hand, expert opinion brought through expert witness testimony can be much more costly, raising concerns about access to justice and resource disparities between participants in litigation.

81.  While Canadian courts have expressed a preference for social science evidence to be presented via expert testimony (R v Spence, para. 68 (Can)), such research has at times been independently reviewed by the court (see, eg, R v Parks (Can)), and is often cited by interveners, who play a similar role to amici in the US.

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