The notion of burden of proof determines which party is responsible to prove an assertion made in judicial proceedings.1 On the other hand, the standard of proof defines how much evidence is needed to establish either an individual issue or the party’s case as a whole.2 In the sense of Article 38(1)(c) of the Statute of the International Court of Justice, the general principle regarding the burden of proof stems from the maxim onus probandi actori incumbit, namely “he who asserts must prove”;3 the said maxim is considered to be a general principle of international law itself.4 The onus probandi principle is a risk-defining rule, since the party who finally must prove a fact takes the risk of its non-establishment.5
II. International practice
The aforementioned principle is widely recognized in international adjudication. Yet, most of the procedural rules employed in international arbitral practice do not contain any provision in relation to the burden of proof, with rare exceptions provided.6 In some jurisdictions, the burden of proof is considered as part of the substantive law, while in others is considered as part of their procedural laws. In a similar vein, there is no uniformity on the application of burden of proof in common law and civil law systems.
III. Allocation of burden of proof
In general, the burden of affirmatively establishing the elements of an assertion rests upon the party alleging them, whether it is the claimant or respondent.7 Due to this, the burden of proof usually lies with the claimant according to the said principle because it is the party asserting the claim.8 In any event, a variety of rules regarding allocation have been observed in international adjudication. For example, in common law systems, the rule on allocation includes the burden of production, as well as the burden of persuasion,9 which remains largely irrelevant in civil law systems.
Following the common law model, it is important to distinguish between the legal and the evidential burden of proof. The legal burden never shifts; by contrast, the evidential burden may shift, depending upon the state of evidence.10 The allocation of the burden, however, remains more problematic in terms of jurisdiction rather than the merits.11
Metal-Tech Ltd. v. Republic of Uzbekistan, ICSID Case No. ARB/10/3, Award, 4 October 2013, para. 237; Limited Liability Company Amto v. Ukraine, SCC Case No. 080/2005, Final Award, 26 March 2008, para. 64; Churchill Mining and Planet Mining Pty Ltd v. Republic of Indonesia, ICSID Case No. ARB/12/40 and 12/14, Award, 6 December 2016, para. 238; International Thunderbird Gaming Corporation v. The United Mexican States, Arbitral Award, 26 January 2006, para. 95; Saipem S.p.A. v. People's Republic of Bangladesh, ICSID Case No. ARB/05/07, Award, 30 June 2009, para. 113; Zhinvali Development Ltd. v. Republic of Georgia, ICSID Case No. ARB/00/1, Award, 24 January 2003, para. 309; Bernhard von Pezold and others v. Republic of Zimbabwe, ICSID Case No. ARB/10/15, Award, 28 July 2015, para. 174; Conocophillips Petrozuata B.V., Conocophillips Hamaca B.V. and Conocophillips Gulf of Paria B.V. v. Bolivarian Republic of Venezuela, ICSID Case No. ARB/07/30, Award, 8 March 2019, para. 272; Azurix Corp. v. the Argentine Republic, ICSID Case No. ARB/01/12, Decision on the Application for Annulment of the Argentine Republic, 1 September 2009, para. 215; Georg Gavrilovic and Gavrilovic d.o.o. v. Republic of Croatia, ICSID Case No ARB/12/39, Award, 26 July 2018, para. 230; Quiborax S.A., Non Metallic Minerals S.A. and Allan Fosk Kaplún v. Plurinational State of Bolivia, ICSID Case No ARB/06/2, Decision on Jurisdiction, 27 September 2012, para. 259.
Middle East Cement Shipping and Handling Co. v. Arab Republic of Egypt, ICSID Case No. ARB/99/6, Award, 12 April 2002, para. 89; Tokios Tokelés v. Ukraine, ICSID Case No. ARB/02/18, Award, 26 July 2007, para. 121; Tradex Hellas S.A. v. Republic of Albania, ICSID Case No. ARB/94/2, Award, 29 April 1999, para. 74; Salini Costruttori S.p.A. and Italstrade S.p.A. v. Hashemite Kingdom of Jordan, ICSID Case No. ARB/02/13, Award, 31 January 2006, para. 70; Generation Ukraine Inc. v. Ukraine, ICSID Case No. ARB/00/9, Award, 16 September 2003, para. 19.1; Noble Ventures, Inc. v. Romania, ICSID Case No. ARB/01/11, Award, 12 October 2005, para. 100; Asian Agricultural Products Ltd. (AAPL) v. Republic of Sri Lanka, ICSID Case No. ARB/87/3, Award, 27 June 1990, para. 56; Ceskoslovenska Obchodni Banka, a.s. v. The Slovak Republic, ICSID Case No. ARB/97/4, Award, 29 December 2004, para. 225; Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), Judgment - Jurisdiction of the Court and Admissibility of the Application, 26 November 1984, para. 101.
For the purposes of jurisdiction, tribunals tend to assess whether a claimant’s case is reasonably arguable on its face.12 Although the respondent is the party challenging jurisdiction, it is for the claimant to prove the opposite, so the legal burden of proof continues to be borne by the latter. Nevertheless, the evidential burden may be shifted to the respondent in case where the claimant is asked to prove a negative13 or when the respondent itself raises defenses,14 whereas the legal burden still lies with the respondent when it comes to proving an affirmative defense.15
Amco Asia Corporation and others v. Republic of Indonesia, ICSID Case No. ARB/81/1, Decision on Jurisdiction, 25 September 1983, para. 38; Emilio Agustín Maffezini v. The Kingdom of Spain, ICSID Case No. ARB/97/7, Decision of the Tribunal on Objections to Jurisdiction, 25 January 2000, para. 69; Azurix Corp. v. The Argentine Republic (I), ICSID Case No. ARB/01/12, Decision on Jurisdiction, 8 December 2003, para. 76; SGS Société Générale de Surveillance S.A. v. Islamic Republic of Pakistan, ICSID Case No. ARB/01/13, Decision on Jurisdiction, 6 August 2003, para. 145; SGS Société Générale de Surveillance S.A. v. Republic of the Philippines, ICSID Case No. ARB/02/6, Decision of the Tribunal on Objections to Jurisdiction, 29 January 2004, para. 26; Siemens A.G. v. The Argentine Republic, ICSID Case No. ARB/02/8, Decision on Jurisdiction, 3 August 2004, para. 180; Joy Mining Machinery Limited v. Arab Republic of Egypt, ICSID Case No. ARB/03/11, Award on Jurisdiction, 6 August 2004, para. 29; Salini Costruttori S.p.A. and Italstrade S.p.A. v. Hashemite Kingdom of Jordan, ICSID Case No. ARB/02/13, Decision on Jurisdiction, 29 November 2004, para. 151; Bayindir Insaat Turizm Ticaret Ve Sanayi A.S. v. Islamic Republic of Pakistan, ICSID Case No. ARB/03/29, Decision on Jurisdiction, 14 November 2005, para. 197.
Ambiente Ufficio S.p.A. and others (formerly Giordano Alpi and others) v. Argentine Republic, ICSID Case No. ARB/08/9, Decision on Jurisdiction and Admissibility, 8 February 2013, para. 312; Waguih Elie George Siag and Clorinda Vecchi v. Arab Republic of Egypt, ICSID Case No. ARB/05/15, Award, 1 June 2009, para. 317.
Waguih Elie George Siag and Clorinda Vecchi v. Arab Republic of Egypt, ICSID Case No. ARB/05/15, Award, 1 June 2009, para. 315; Chevron Corporation and Texaco Petroleum Company v. The Republic of Ecuador (I), PCA Case No. 2007-02/AA277, Interim Award, 1 December 2008, para. 138; Pac Rim Cayman LLC v. The Republic of El Salvador, ICSID Case No. ARB/09/12, Decision on the Respondent's Jurisdictional Objections, 1 June 2012, para. 2.13.
The approach to merits is the same as jurisdiction concerning the onus probandi principle. Applying the distinction between the legal and evidential burden, in a case where a party proves prima facie the asserted facts, the burden of proof may shift to the other party (speaking from an evidential perspective).16 Additionally, it may also shift when a party cannot fully prove something but can demonstrate that the other party has access or control over the missing evidence, in the name of fairness and good faith.17
In any event, the shifting of the burden of proof remains a delicate issue especially since the responding party is a State; for instance, in cases of “inferences of fact” or “circumstantial evidence”, a tribunal would rarely shift the burden of proof.18 Reasons as such have given rise to an opposite view having been supported by some tribunals, meaning that the allocation of burden of proof is an absolute.19
Middle East Cement Shipping and Handling Co. v. Arab Republic of Egypt, ICSID Case No. ARB/99/6, Award, 12 April 2002, para. 94; United States – Measures Affecting Imports of Woven Wool Shirts and Blouses from India, Adopted 23 May 1997, WT/DS33/AB/R, p. 14; Marvin Roy Feldman Karpa v. United Mexican States, ICSID Case No. ARB(AF)/99/1, Award, 16 December 2002, para. 177; Asian Agricultural Products Ltd. (AAPL) v. Republic of Sri Lanka, ICSID Case No. ARB/87/3, Award, 27 June 1990, para. 56; International Thunderbird Gaming Corporation v. The United Mexican States, Arbitral Award, 26 January 2006, para. 95; Ioannis Kardassopoulos v. Georgia, ICSID Case No. ARB/05/18, Award, 3 March 2010, para. 230; RosInvestCo UK Ltd. v. The Russian Federation, SCC Case No. 079/2005, Final Award, 12 September 2010, para. 250; Eli Lilly and Company v. Government of Canada, ICSID Case No. UNCT/14/2, Final Award, 16 March 2017, para. 109; Karkey Karadeniz Elektrik Uretim A.S. v. Islamic Republic of Pakistan, ICSID Case No. ARB/13/1, Award, 22 August 2017, para. 497.
The Rompetrol Group N.V. v. Romania, ICSID Case No. ARB/06/3, Award, 6 May 2013, para. 178; Jan Oostergetel and Theodora Laurentius v. The Slovak Republic, Final Award, 23 April 2012, para. 148; United Parcel Service of America, Inc. (UPS) v. Government of Canada, ICSID Case No. UNCT/02/1, Award on the Merits, 24 May 2007, para. 84.
C. ICSID procedure
Böckstiegel, K., Presenting Evidence in International Arbitration, ICSID Review-Foreign Investment Law Journal, Vol. 16, Issue 1, 2001, pp. 1–9.
Born, G., Chapter 4: On Burden and Standard of Proof, in Kinnear, M., Fischer, G.R. et al. (eds), Building International Investment Law: The First 50 Years of ICSID, Kluwer Law International, 2015, pp. 43-54.
Brown, Ch., A Common Law of International Adjudication, Oxford University Press, 2007, pp. 93-98.
Schreuer, Ch. et al., The ICSID Convention: A Commentary, 2nd ed., Cambridge University Press, 2009, pp. 669-670.
Sourgens, F., Evidence in Investor-State Arbitration – The Need for Action, Kluwer Arbitration Blog, 2017.