1 See: The IBA Arbitration Guidelines and Rules Subcommittee, ‘Report on the Reception of the IBA Arbitration Soft Law Products’ (International Bar Association, 2016) paras 46–48 <www.ibanet.org/Document/Default.aspx?DocumentUid=105d29a3-6261-4437-84e2-1c8637844beb> accessed 27 November 2018 (hereafter ‘2016 IBA Report’). It should be noted that the distribution of references to different provisions of the IBA Rules varies according to jurisdiction.
2 IBA Rules on the Taking of Evidence in International Commercial Arbitration 1999, Article 9.
5 See SCC Rules, Article 31(1); DIAC Rules, Article 28.2; SIAC Rules, Rule 19.2; LCIA Rules, Article 22.1(vi); PCA Rules, Article 27.4; WIPO Arbitration Rules, Article 50(a); PRIME Finance Arbitration Rules, Article 27.4; ADR Institute of Canada (ADRIC) Arbitration Rules, Rule 4.19.4; Milan Chamber of Arbitration Rules, Article 25; Commercial Arbitration Centre of the Portuguese Chamber of Commerce and Industry Rules of Arbitration, Article 31.1; Madrid Court of Arbitration Rules of Arbitration, Article 29.3; DIFC–LCIA Rules, Article 22.1(vi); HKIAC Rules, Article 22.2; ICDR Rules, Article 20.6; NAI Rules, Article 26.1.. Interestingly, the ICC Rules do not contain a specific provision to the same effect. Article 25(1) of the ICC Rules simply provides that ‘The arbitral tribunal shall proceed within as short a time as possible to establish the facts of the case by all appropriate means’.
6 German Code of Civil Procedure (Zivilprozessordnung) 2013, s 1042.
7 Belgium Judicial Code 2016, Article 1700, para 3 states that ‘Unless the parties have agreed otherwise, the arbitral tribunal shall have discretion in the rules of evidence to be applied’.
8 Netherlands Code of Civil Procedure 2011, Article 1039(5).
9 See Gary B Born, International Commercial Arbitration (2nd edn, Kluwer Law Arbitration 2014) 2146–49 (hereafter ‘Born’). Born cites U.S. Turnkey Exploration, Inc. v PSI, Inc. 577 So2d 1131, 1135 (La App 1991), in which it was said that: ‘Unless a mode of conducting the proceedings has been prescribed by the arbitration agreement or submissions, or regulated by statute, arbitrators have a general discretion as to the mode of conducting the proceedings and are not bound by formal rules of procedure and evidence and the standard of review of arbitration procedures is merely whether a party to an arbitration has been denied a fundamentally fair hearing’.
10 Born (n 9) 2306–13. Born cites decisions of the United States Courts in which it has been said that ‘[a]rbitrators have broad discretion to make evidentiary decisions’ and that ‘arbitrators are not bound by rules of evidence’; see Int’l Chem. Workers Union v Columbian Chem. Co. 331 F3d 491, 497 (5th Cir. 2003); and Generica Ltd v Pharm. Basics, Inc. 125 F3d 1123, 1130 (7th Cir. 1997).
11 English Arbitration Act 1996, s 34.
12 Jeffrey Waincymer, Procedure and Evidence in International Arbitration (Kluwer Law International 2012) 750–51 (hereafter ‘Waincymer’).
13 IBA Rules (n 3) Preamble 1 and 3. See Chapter 2.
15 Konstantin Pilkov, ‘Evidence in International Arbitration: Criteria for Admission and Evaluation’ (2014) Arbitration 147, 154 (hereafter ‘Pilkov’).
16 These are set out in IBA Rules (n 13) Article 9.2 and are addressed at 12.57– 12.316. See also Chapter 6 paras 6.76–6.146 on the meaning of ‘relevant to the case and material to its outcome’ for the purposes of Article 9.2(a).
18 IBA Rules (n 3) Articles 3.5 and 9.2(a).
19 See further Julian Lew, ‘Chapter 1. Document Disclosure, Evidentiary Value of Documents and Burden of Evidence’ in Teresa Giovannini and Alexis Mourre (eds), Written Evidence and Discovery in International Arbitration: New Issues and Tendencies (Kluwer Law International 2009). For a discussion of how this issue is treated in international arbitration, see Carol Mulcahy, ‘What Does it Mean? Contractual Interpretation in International Commercial Arbitration’ (2015) Dispute Resolution International 15. The standard of admissibility in civil law traditions is said to be lower than in common law jurisdictions; see Anna Kubalczyk, ‘Evidentiary Rules in International Arbitration: A Comparative Analysis of Approaches and the Need for Regulation’ (2015) 3(1) Groningen Journal of International Law 85, s IV (hereafter ‘Kubalczyk’). There are dangers in such generalizations, but certainly the common law approach may derive in part from a concern that certain types of evidence should be excluded because those who decide on the facts (traditionally, in those jurisdictions, a jury of lay people) should not be permitted to consider certain types of evidence for fear that they may attach undue weight to it (for example, hearsay evidence) or because certain interests need to be protected (for example, documents that are confidential in nature or protected by legal privilege).
22 See further Pilkov (n 15) 150–51.
24 ‘Extracts from ICC Case Materials on the Taking of Evidence with References to the IBA Rules’ (2016) 1 ICC Dispute Resolution Bulleting 127 (emphasis added). Waincymer (n 12) 792–800 notes that: ‘International adjudicatory bodies generally consider questions of weight in relation to all submitted evidence and do not wish to hear separate clams as to admissibility’.
25 ibid. The same point is made by other commentators. See, for example, Kubalczyk (n 19).
26 EDF (Services) Limited v Romania (Procedural Order No. 3, 29 August 2008) ICSID Case No. ARB/05/13 – (hereafter ‘EDF v Romania PO3’).
27 Anne Schlaepfer and Philippe Bärtsch, ‘A Few Reflections on the Assessment of Evidence by International Arbitrators’ (2010) International Business Law Journal 217 (hereafter ‘Schlaepfer and Bärtsch’), which references decisions 4A_362/2013 and 4A_448/2013 of the Swiss Supreme Court. For an example of a case where documents leaked online were admitted into evidence, see Caratube International Oil Company LLP and Devincci Salah Hourani v Republic of Kazakhstan ICSID Case No. ARB/13/13. This case is discussed at 12.30.
30 Unpublished decision of the tribunal in Caratube International Oil Company LLP v The Republic of Kazakhstan ICSID Case No. ARB/13/13.
32 IBA Rules (n 3) Articles 3.3 and 9.
33 ‘Hot-tubbing’, or witness conferencing, is a technique in which two or more fact or expert witnesses presented by one or more of the parties are questioned together on particular topics by the arbitral tribunal and possibly by counsel. See further ICC Arbitration Commission Report on Controlling Time and Costs in Arbitration (International Chamber of Commerce 2018) para 79. See Chapter 11 paras 11.72–11.74. See also Guidelines for Witness Conferencing in International Arbitration (Chartered Institute of Arbitrators, 2019).
34 See, for example, the statement by the tribunal in EDF v Romania PO3 (n 26)  that ‘An obvious condition for the admissibility of evidence is its reliability and authenticity. It would be a waste of time and money to admit evidence that is not and cannot be authenticated’.
36 Hearsay evidence is a written or oral statement made otherwise than by a witness giving their own first-hand evidence in proceedings, which is tendered as evidence of the matters stated and which is relied on to prove the truth of those matters.
37 Born (n 9) 2306–13. For discussion about destruction of documents see 12.258– 12.274 for more detail.
38 See further Pilkov (n 15) 152 and citing Audun Jøsang and Viggo Bondi, ‘Legal Reasoning with Subjective Logic’ (2000) Artificial Intelligence and Law 289.
39 Arduina Holdings BV v Celtic Resources Holding plc  EWHC 3155 (Comm) –. See also London Underground Limited v Citylink Telecommunications Limited  EWHC 1749 (TCC) , and Sonatrach v Statoil  EWHC 875 (Comm) –.
40 IBA Rules (n 3) Articles 9.5 and 9.6; see also Article 9.1.
42 ‘Each party shall bear the burden of proving the facts on which it relies to support its claim, defense or counterclaim and provide the basis for its opinions, arguments and counter-arguments’.
43 ‘Each party shall have the burden of proving the facts relied on to support its claim or defence’.
44 ‘Each party shall have the burden of proving the facts relied on to support its claim or defence’.
45 ‘Each party shall have the burden of proving the facts relied on to support its claim or defence’.
46 See further Born (n 9) 2313–15.
47 The issue of burden of proof was not dealt with in the UNCITRAL Model Law on International Commercial Arbitration (as adopted by UNCITRAL on 21 June 1985 and as amended by UNCITRAL on 7 July 2006) (hereafter ‘UNCITRAL Model Law’) in part because of differences in view between legal families as to whether burden of proof is procedural or substantive. Waincymer (n 12) 762–65. See also Anne Véronique Schläpfer, ‘The Burden of Proof in International Arbitration’ in Albert Jan van den Berg (ed), Legitimacy: Myths, Realities, Challenges (Kluwer Law International 2015). The position is complex. For example, Lord Collins of Mapesbury and others (eds), Dicey, Morris and Collins on The Conflict of Laws (15th edn, Sweet & Maxwell 2012) para 7-034 notes that, ‘Although there is some authority for the proposition that at common law, questions relating to the burden of proof are matters for the lex fori, there is much to be said for treating them as substantive’ (footnote omitted). See further Lotfi (n 41) s II.
48 For example, as a matter of English law, unless otherwise provided by statute, questions of evidence are generally determined by the lex fori and not by the law governing the substantive issue selected by English rules as to conflict of laws. See Hodge Malek and others (eds), Phipson on Evidence (19th edn, Sweet & Maxwell 2013) para 1–26. Under German law, the burden of proof appears to be primarily dealt with as part of substantive law, although procedural law may also have an impact. For example, in relation to the former position, German Civil Code (Bürgerliches Gesetzbuch) 2013, s 363 provides that: ‘Burden of proof in the case of acceptance as performance of contract: If the obligee has accepted performance offered to him as performance of contract, he bears the burden of proof if he does not wish to have the performance considered as performance of contract because it was different from the performance owed or because it was incomplete’. However, with reference to the second category, German Code of Civil Procedure, s 287 provides that the court may ‘estimate the amount of damages on the basis of the court’s discretion, based on its evaluation of all circumstances’ (emphasis added), an approach that is said to relax the burden of proof. Annette Keilmann, ‘How to Prove Your Case: Conflict between Substantive and Procedural Law in International arbitration?’ (Global Arbitration News, 31 March 2016) <https://globalarbitrationnews.com/how-to-prove-your-case-conflict-between-substantive-and-procedural-law-in-international-arbitration-20160324/> accessed 4 December 2018. The author also draws attention to the potential consequences of adopting the substantive provisions of a national system without also taking account of the procedural corollary that may exist in that jurisdiction.
50 Born (n 9) 2315. See also Sigvard Jarvin, ‘The Sources and Limits of the Arbitrator’s Powers’ (1986) Arbitration International 140, 151, who suggests that where parties and counsel come from different legal traditions the tribunal should adopt an approach that is fair to all sides: ‘The arbitrators, faced with parties and counsel from different legal systems, used to different principles with regard to the burden of proof, and presentation of evidence, should try to find a middle way which can be applied by both sides and thus achieve fairness for both of them. The strict distribution of the burden of proof applied by national courts does not apply in international arbitration’.
51 See further Waincymer (n 12) 762–66.
53 See, for example, SIAC Rules, Rule 29.1: ‘A Party may apply to the Tribunal for the early dismissal of a claim or defence on the basis that: (a) a claim or defence is manifestly without legal merit; or (b) a claim or defence is manifestly outside the jurisdiction of the Tribunal’. See also (well-established) ICSID Arbitration Rules 2006, Rule 41(5) in similar terms.
54 A recent analysis and commentary on tribunal practice in relation to ICSID Arbitration Rules, Rule 41(5) contains an interesting discussion on the extent to which tribunals should and do assume that the facts underlying the legal claim are as stated and (in summary) the circumstances in which it might be permissible to dismiss on the basis that the facts as stated are plainly unsustainable and the benchmark to be applied to reach that conclusion. See Michele Potestà, ‘Chapter 9: Preliminary Objections to Dismiss Claims that Are Manifestly Without Legal Merit under Rule 41(5) of the ICSID Arbitration Rules’ in Crina Baltag (ed), ICSID Convention after 50 Years: Unsettled Issues (Kluwer Law International 2016).
56 Waincymer (n 12) 766–71 concludes that, despite some comments to the contrary, there is unlikely to be any difference between the two formulations—the real test in each case must be a test of preponderance of evidence. No system allows a party to succeed if their opponent’s contentions are preferred. See also Lotfi (n 41) s II. See also Pilkov (n 15) 153, who opines that, in assessing the sufficiency of the evidence, the tribunal must ‘determine whether there is a valid line of reasoning and permissible inferences which could lead a rational person to the conclusion reached by the arbitrator on the basis of the evidence’.
58 Schlaepfer and Bärtsch (n 27) 217.
59 See further Born (n 9) 2306–15 and Waincymer (n 12) 775–78.
60 The difficulties associated with this exercise are addressed at 12.368– 12.374.
61 In an international law context, circumstantial evidence has been described in a dissenting judgment of the International Court of Justice as: ‘facts which, while not supplying immediate proof of the charge, yet make the charge probable with the assistance of reasoning’; Waincymer (n 12) 793–94, citing the dissenting opinion of Judge Badawi Pash in the Corfu Channel Case, United Kingdom of Great Britain v People’s Republic of Albania (Merits) (1949) ICJ Reports 4, 18.
63 See IBA Rules (n 3) Articles 3.5, 3.9, 3.10, 4.10, 6.3, 7, 8.2, and 8.5.
64 1999 IBA Working Party and 2010 IBA Rules of Evidence Review Subcommittee, ‘Commentary on the Revised Text of the 2010 IBA Rules on the Taking of Evidence in International Arbitration’ (International Bar Association, 2014) 25 <www.ibanet.org/Document/Default.aspx?DocumentUid=DD240932-0E08-40D4-9866-309A635487C0> accessed 27 November 2018 (hereafter ‘Commentary on the IBA Rules’) confirms the discretion of the tribunal to determine the objections: ‘While the provision states that the arbitral tribunal “shall” exclude evidence meeting one of the specified exceptions (including relevance and materiality) the arbitral tribunal obviously retains its discretion to determine whether one of the specified criteria has been met’.
65 See Hilmar Raeschke-Kessler, ‘The Production of Documents in International Arbitration: Commentary on Article 3 of the New IBA Rules of Evidence’ (2002) Arbitration International 411 (hereafter ‘Raeschke-Kessler’).