65. The Appeals Chamber notes that it has been the practice of this Tribunal and of the International Criminal Tribunal for Rwanda (“ICTR”)[1] to accept as evidence the testimony of a single witness on a material fact without need for corroboration. […]  

At paragraphs 91 to 97, the Appeals Chamber examined the conditions under which armed forces fighting against the central authorities of the same State in which they live and operate may be deemed to act on behalf of another State, in other words, the conditions under which those forces may be assimilated to the organs of a State other than that on whose territory they live and operate. It concluded:

96. […] [I]n cases such as that currently under discussion, what is required for criminal responsibility to arise is some measure of control by a Party to the conflict over the perpetrators.[1]

97. It is nevertheless imperative to specify what degree of authority or control must be wielded by a foreign State over armed forces fighting on its behalf in order to render international an armed conflict which is prima facie internal.  Indeed, the legal consequences of the characterisation of the conflict as either internal or international are extremely important.  Should the conflict eventually be classified as international, it would inter alia follow that a foreign State may in certain circumstances be held responsible for violations of international law perpetrated by the armed groups acting on its behalf.  

At paragraph 98 the Appeals Chamber gave the following explanation for the need to supplement international humanitarian law general international law rules concerning the criteria for considering individuals to be acting as de facto state organs:

98. International humanitarian law does not contain any criteria unique to this body of law for establishing when a group of individuals may be regarded as being under the control of a State, that is, as acting as de facto State officials.[2]  Consequently, it is necessary to examine the notion of control by a State over individuals, laid down in general international law, for the purpose of establishing whether those individuals may be regarded as acting as de facto State officials.  This notion can be found in those general international rules on State responsibility which set out the legal criteria for attributing to a State acts performed by individuals not having the formal status of State officials.

In the course of a review of the relevant rules of general international law in paragraphs 99–144, the Appeals Chamber observed:

120. One should distinguish the situation of individuals acting on behalf of a State without specific instructions, from that of individuals making up an organised and hierarchically structured group, such as a military unit or, in case of war or civil strife, armed bands of irregulars or rebels.  Plainly, an organised group differs from an individual in that the former normally has a structure, a chain of command and a set of rules as well as the outward symbols of authority. Normally a member of the group does not act on his own but conforms to the standards prevailing in the group and is subject to the authority of the head of the group. Consequently, for the attribution to a State of acts of these groups it is sufficient to require that the group as a whole be under the overall control of the State.

The Appeals Chamber concluded:

137. In sum, the Appeals Chamber holds the view that international rules do not always require the same degree of control over armed groups or private individuals for the purpose of determining whether an individual not having the status of a State official under internal legislation can be regarded as a de facto organ of the State.  The extent of the requisite State control varies.  Where the question at issue is whether a single private individual or a group that is not militarily organised has acted as a de facto State organ when performing a specific act, it is necessary to ascertain whether specific instructions concerning the commission of that particular act had been issued by that State to the individual or group in question; alternatively, it must be established whether the unlawful act had been publicly endorsed or approved ex post facto by the State at issue.  By contrast, control by a State over subordinate armed forces or militias or paramilitary units may be of an overall character (and must comprise more than the mere provision of financial assistance or military equipment or training).  This requirement, however, does not go so far as to include the issuing of specific orders by the State, or its direction of each individual operation. Under international law it is by no means necessary that the controlling authorities should plan all the operations of the units dependent on them, choose their targets, or give specific instructions concerning the conduct of military operations and any alleged violations of international humanitarian law.  The control required by international law may be deemed to exist when a State (or, in the context of an armed conflict, the Party to the conflict) has a role in organising, coordinating or planning the military actions of the military group, in addition to financing, training and equipping or providing operational support to that group.  Acts performed by the group or members thereof may be regarded as acts of de facto State organs regardless of any specific instruction by the controlling State concerning the commission of each of those acts.

229. In light of the preceding propositions it is now appropriate to distinguish between acting in pursuance of a common purpose or design to commit a crime, and aiding and abetting. 

(i) The aider and abettor is always an accessory to a crime perpetrated by another person, the principal.

(ii) In the case of aiding and abetting no proof is required of the existence of a common concerted plan, let alone of the pre-existence of such a plan.  No plan or agreement is required: indeed, the principal may not even know about the accomplice’s contribution.

(iii) The aider and abettor carries out acts specifically directed to assist, encourage or lend moral support to the perpetration of a certain specific crime (murder, extermination, rape, torture, wanton destruction of civilian property, etc.), and this support has a substantial effect upon the perpetration of the crime.  By contrast, in the case of acting in pursuance of a common purpose or design, it is sufficient for the participant to perform acts that in some way are directed to the furthering of the common plan or purpose.

(iv) In the case of aiding and abetting, the requisite mental element is knowledge that the acts performed by the aider and abettor assist the commission of a specific crime by the principal.  By contrast, in the case of common purpose or design more is required (i.e., either intent to perpetrate the crime or intent to pursue the common criminal design plus foresight that those crimes outside the criminal common purpose were likely to be committed), as stated above.

228.  By contrast, the mens rea element differs according to the category of common design under consideration.  With regard to the first category, what is required is the intent to perpetrate a certain crime  (this being the shared intent on the part of all co-perpetrators).  With regard to the second category (which, as noted above, is really a variant of the first), personal knowledge of the system of ill-treatment is required (whether proved by express testimony or a matter of reasonable inference from the accused’s position of authority), as well as the intent to further this common concerted system of ill-treatment.  With regard to the third category, what is required is the intention to participate in and further the criminal activity or the criminal purpose of a group and to contribute to the joint criminal enterprise or in any event to the commission of a crime by the group.  In addition, responsibility for a crime other than the one agreed upon in the common plan arises only if, under the circumstances of the case, (i) it was foreseeable that such a crime might be perpetrated by one or other members of the group and (ii) the accused willingly took that risk.

43. Article 20(1) of the Statute provides that “[t]he Trial Chambers shall ensure that a trial is fair and expeditious […]”. This provision mirrors the corresponding guarantee provided for in international and regional human rights instruments:  the International Covenant on Civil and Political Rights (1966) (“ICCPR”),[1] the European Convention on Human Rights (1950),[2] and the American Convention on Human Rights (1969).[3]  The right to a fair trial is central to the rule of law: it upholds the due process of law.  The Defence submits that due process includes not only formal or procedural due process but also substantive due process.[4]

44. The parties do not dispute that the right to a fair trial guaranteed by the Statute covers the principle of equality of arms.  This interpretation accords with findings of the Human Rights Committee (“HRC”) under the ICCPR.  The HRC stated in Morael v. France[5] that a fair hearing under Article 14(1) of the ICCPR must at a minimum include, inter alia, equality of arms.  Similarly, in Robinson v. Jamaica[6] and Wolf v. Panama[7] the HRC found that there was inequality of arms in violation of the right  to a fair trial under Article 14(1) of the ICCPR.  Likewise, the case law under the ECHR cited by the Defence accepts that the principle is implicit in the fundamental right of the accused to a fair trial.  The principle of equality of arms between the prosecutor and accused in a criminal trial goes to the heart of the fair trial guarantee.  The Appeals Chamber finds that there is no reason to distinguish the notion of fair trial under Article 20(1) of the Statute from its equivalent in the ECHR and ICCPR, as interpreted by the relevant judicial and supervisory treaty bodies under those instruments. Consequently, the Chamber holds that the principle of equality of arms falls within the fair trial guarantee under the Statute.

46. The Defence contends that the minimum guarantee in Article 21(4)(b) of the Statute to adequate time and facilities for the preparation of defence at trial forms part of the principle of equality of arms, implicit in Article 20(1).  It argues that, since the authorities in the Republika Srpska failed to cooperate with the Defence, the Appellant did not have adequate facilities for the preparation of his defence, thereby prejudicing his enjoyment of equality of arms.

47. The Appeals Chamber accepts the argument of the Defence that, on this point, the relationship between Article 20(1) and Article 21(4)(b) is of the general to the particular.  It also agrees that, as a minimum, a fair trial must entitle the accused to adequate time and facilities for his defence.  

In order to decide on the scope of application of the principle of equality of arms, the Appeals Chamber  carried out a review of the international case-law in paragraphs 48–50. It then continued as follows:-

51. The case law mentioned so far relates to civil or criminal proceedings before domestic courts.  These courts have the capacity, if not directly, at least through the extensive enforcement powers of the State, to control matters that could materially affect the fairness of a trial.  It is a different matter for the International Tribunal.  The dilemma faced by this Tribunal is that, to hold trials, it must rely upon the cooperation of States without having the power to compel them to cooperate through enforcement measures.[8] The Tribunal must rely on the cooperation of States because evidence is often in the custody of a State and States can impede efforts made by counsel to find that evidence.  Moreover, without a police force, indictees can only be arrested or transferred to the International Tribunal through the cooperation of States or, pursuant to Sub-rule 59bis, through action by the Prosecution or the appropriate international bodies.  Lacking independent means of enforcement, the ultimate recourse available to the International Tribunal in the event of failure by a State to cooperate, in violation of its obligations under Article 29 of the Statute, is to report the non-compliance to the Security Council.[9]

52. In light of the above considerations, the Appeals Chamber is of the view that under the Statute of the International Tribunal the principle of equality of arms must be given a more liberal interpretation than that normally upheld with regard to proceedings before domestic courts.  This principle means that the Prosecution and the Defence must be equal before the Trial Chamber.  It follows that the Chamber shall provide every practicable facility it is capable of granting under the Rules and Statute when faced with a request by a party for assistance in presenting its case.  The Trial Chambers are mindful of the difficulties encountered by the parties in tracing and gaining access to evidence in the territory of the former Yugoslavia where some States have not been forthcoming in complying with their legal obligation to cooperate with the Tribunal.  Provisions under the Statute and the Rules exist to alleviate the difficulties faced by the parties so that each side may have equal access to witnesses.  The Chambers are empowered to issue such orders, summonses, subpoenas, warrants and transfer orders as may be necessary for the purposes of an investigation or for the preparation or conduct of the trial.  This includes the power to:

(1) adopt witness protection measures, ranging from partial to full protection;

(2) take evidence by video-link or by way of deposition;

(3) summon witnesses and order their attendance;

(4) issue binding orders to States for, inter alia, the taking and production of evidence; and

(5) issue binding orders to States to assist a party or to summon a witness and order his or her attendance under the Rules.

A further important measure available in such circumstances is:

(6) for the President of the Tribunal to send, at the instance of the Trial Chamber, a request to the State authorities in question for their assistance in securing the attendance of a witness.

In addition, whenever the aforementioned measures have proved to be to no avail, a Chamber may, upon the request of a party or proprio motu:

(7) order that proceedings be adjourned or, if the circumstances so require, that they be stayed. 

55. The Appeals Chamber can conceive of situations where a fair trial is not possible because witnesses central to the defence case do not appear due to the obstructionist efforts of a State.  In such circumstances, the defence, after exhausting all the other measures mentioned above, has the option of submitting a motion for a stay of proceedings. The Defence opined during the oral hearing that the reason why such action was not taken in the present case may have been due to trial counsel’s concern regarding the long period of detention on remand.  The Appeals Chamber notes that the Rules envision some relief in such a situation, in the form of provisional release, which, pursuant to Sub-rule 65(B),[1] may be granted “in exceptional circumstances”.  It is not hard to imagine that a stay of proceedings occasioned by the frustration of a fair trial under prevailing trial conditions would amount to exceptional circumstances under this rule. The obligation is on the complaining party to bring the difficulties to the attention of the Trial Chamber forthwith so that the latter can determine whether any assistance could be provided under the Rules or Statute to relieve the situation.  The party cannot remain silent on the matter only to return on appeal to seek a trial de novo, as the Defence seeks to do in this case.

24. […] [Article 21(4)(e)] serves to ensure that the accused is placed in a position of procedural equality in respect of obtaining the attendance and examination of witnesses with that of the Prosecution.  In other words, the same set of rules must apply to the right of the two parties to obtain the attendance and examination of witnesses.  It does not follow from Article 21(4)(e) that the application of the relevant rules has to result in the witnesses of the two parties giving evidence in exactly the same manner.  Thus, the Appellant’s understanding of his right as embodied in Article 21(4)(e) of the Statute appears to rest on a misconception when he contends that, since all the witnesses for the Prosecution were heard directly before the Trial Chamber, that gives him an automatic right to have all his witnesses heard directly before the Trial Chamber as well.

23. Article 21 of the Statute […] has been interpreted in many Decisions of the Tribunal as having been based upon the well-known international law principle of "equality of arms". There has, however, been some difference of opinion expressed as to whether the principle relates only to the position of the accused – that is, that it provides merely that the accused is to be afforded the same rights as the Prosecution – or whether it relates to equality between both parties. […]

[…]

25. This application of the concept of a fair trial in favour of both parties is understandable […]. [I]t is difficult to see how a trial could ever be considered to be fair where the accused is favoured to the expense of the Prosecution […].

30.     Review proceedings under Article 26 of the Statute and Rule 119 are different from appellate proceedings under Article 25 and Rule 115. Where an applicant seeks to present a new fact which becomes known only after trial, despite the exercise of due diligence during the trial in discovering it, Rule 119 is the governing provision. In such a case, the Appellant is not seeking to admit additional evidence of a fact that was considered at trial, but rather a new fact. The proper venue for a review application is the Chamber that rendered the final judgement; it is to that Chamber that the motion for review should be made. In this case, it is for the Trial Chamber to review the Judgement and determine whether the new fact, if proved, could have been a decisive factor in reaching a decision.

[…]

32.     The Appeals Chamber will, however, observe that a distinction exists between a fact and evidence of that fact. The mere subsequent discovery of evidence of a fact which was known at trial is not itself a new fact within the meaning of Rule 119 of the Rules. […]

See also paras 36, 42.

36.     Rule 115 (A) provides that a “party may apply by motion to present before the Appeals Chamber additional evidence which was not available to it at the trial”. That relates to appeals. Rule 119 enables a party to seek a review “[w]here a new fact has been discovered which was not known to the moving party at the time of the proceedings before a Trial Chamber or the Appeals Chamber, and could not have been discovered through the exercise of due diligence”. The Appellant submits that the reference to “diligence” in the latter but not in the former means that diligence is not required under Rule 115. However, whilst the Rules can illustrate the meaning of the Statute under which they are made, they cannot vary the Statute. If there is a variance, it is the Statute which prevails. But, for the reasons explained below, there is no variance in this case. In the view of the Appeals Chamber, there is a requirement for the exercise of due diligence by a party moving under Rule 115.

37.     Article 25, paragraph 1, of the Statute provides for appeals on two grounds, namely, “an error on a question of law invalidating the decision” and “an error of fact which has occasioned a miscarriage of justice”. The first error is clearly an error committed by the Trial Chamber. That, in principle, would seem to be also the case with the second error. But it is difficult to see how the Trial Chamber may be said to have committed an error of fact where the basis of the error lies in additional evidence which, through no fault of the Trial Chamber, was not presented to it. Where evidence was sought to be presented to the Trial Chamber but was wrongly excluded by it, there is no need for recourse to the provisions relating to the production of additional evidence to the Appeals Chamber; there the Trial Chamber would have committed an error appealable in the ordinary way.

38.     It is only by construing the reference to “an error of fact” as meaning objectively an incorrectness of fact disclosed by relevant material, whether or not erroneously excluded by the Trial Chamber, that additional material may be admitted. Such an extension of the concept of an “error of fact” as being not restricted to an error committed by the Trial Chamber may be required by justice; but justice would also require the accused to show why the additional evidence could not be presented to the Trial Chamber in exercise of the rights expressly given to him by the Statute. It would be right to hold that the purpose of the Statute in giving those rights was that the accused should exercise due diligence in utilising them. This would exclude cases in which the failure to exercise those rights was due to lack of diligence.

[…]

40.     The compulsory and protective machinery of the International Tribunal may not always be able to give total assurance that witnesses will be both available and protected if necessary. That is all the more reason why the machinery at the disposal of the International Tribunal should be used. A party seeking leave to present additional evidence should show that it has sought protection for witnesses from the Trial Chamber where appropriate, and that it has requested the Trial Chamber to utilise its powers to compel witnesses to testify if appropriate. Any difficulties, including those arising from intimidation or inability to locate witnesses, should be brought to the attention of the Trial Chamber.

[…]

42.     By the time proceedings have reached the Appeals Chamber, evidence relevant to the culpability of the accused has already been submitted to a Trial Chamber to enable it to reach a verdict and a sentence, if he is found guilty. From the judgement of the Trial Chamber there lies an appeal to the Appeals Chamber. The corrective nature of that procedure alone suggests that there is some limitation to any additional evidentiary material sought to be presented to the Appeals Chamber; otherwise, the unrestricted admission of such material would amount to a fresh trial. Further, additional evidence should not be admitted lightly at the appellate stage, considering that Rule 119 provides a remedy in circumstances in which new facts are discovered after the trial.

43.     Consideration may be given to the consequences of the opposite holding that additional evidence may be presented to the Appeals Chamber even where, through lack of diligence, it was not presented to the Trial Chamber though available. The Prosecutor can appeal from an acquittal. She may seek to reverse the acquittal on the basis of an error of fact disclosed by additional evidence. If the additional evidence was available to her but not presented to the Trial Chamber through lack of diligence, the accused is in effect being tried a second time. In substance, the non bis in idem prohibition is breached.

44.     The Appeals Chamber therefore finds that the position under the Statute is as indicated above and cannot be cut down by reference to any apparent discrepancy in the wording of Rules 115 and 119 of the Rules. The word “apparent” is used because, on a proper construction, Rule 115 is to be read in the light of the Statute; it is therefore subject to requirements of the Statute which have the effect of imposing a duty to be reasonably diligent. Where evidence is known to an accused person, but he fails through lack of diligence to secure it for the Trial Chamber to consider, he is of his own volition declining to make use of his entitlements under the Statute and of the machinery placed thereunder at his disposal; he certainly cannot complain of unfairness.

45.     In summary, additional evidence is not admissible under Rule 115 in the absence of a reasonable explanation as to why it was not available at trial. Such an explanation must include compliance with the requirement that the moving party exercised due diligence. This conclusion is consistent with the Statute and with the jurisprudence of many countries; it is not, however, dependent on that jurisprudence.

[…]

3.       Material which existed at trial but of which the Defence was unaware

[…]

58.     […] While the Defence is required to use due diligence to identify and seek out witnesses, there are limits to this obligation. The Appeals Chamber finds that the Appellant has provided sufficient indication that these witnesses and materials were unknown to the Defence, despite the exercise of due diligence, and thus not available at the time of trial […].

4.       Material which the Appellant was unable to adduce at trial

59.     This category relates to witnesses of whom the Defence was aware at the time of trial but whose evidence they were unable to produce. The material under this heading may be divided into three sub-categories: witnesses who were unwilling or unable to come forward at the trial stage, for example, witnesses who were imprisoned at the time; witnesses alleged to have been intimidated; and potential witnesses who could not be located at the time of trial.

60.     First, then, there is the category of potential witnesses who were simply unwilling to come forward at the trial stage but are now willing to do so at the appeal stage. […] No evidence has been submitted to the Appeals Chamber to indicate that any request was made to the Trial Chamber for the issue of subpoenas to compel the attendance of these witnesses. Despite the obvious practical difficulties in obtaining the evidence of such witnesses, a party cannot later seek to have such material admitted as additional evidence unavailable at trial unless it has raised the issue with the Trial Chamber at the time. As discussed above, the requirement of due diligence is not satisfied where there is insufficient attempt to invoke such coercive measures as were at the disposal of the International Tribunal. Therefore, it cannot be said that the evidence of these three witnesses was not available at trial.

[…]

62.     The second category is a substantial one. It relates to potential witnesses who were known to the Defence at the time of trial but who are said to have been intimidated by persons in authority in the former Yugoslavia. […] Again, in the absence of any evidence to demonstrate that attempts were made to obtain such protection for these witnesses as the International Tribunal could offer, the Appeals Chamber finds that reasonable diligence was not exercised. Consequently, the testimony of these witnesses cannot be said to have been unavailable at trial.

[RULE 115 OF THE ICTY RULES WAS SUBSEQUENTLY AMENDED ON 12 July 2002, 30 September 2002, and 21 July 2005]