After reiterating (at paras 297-301) the legal standard set out in the Hadžihasanović and Kubura Appeal Judgement, the Appeals Chamber made the following findings:

303. The Appeals Chamber observes that the Trial Chamber found that prior to the commencement of the attack against Srđ, Strugar had reason to know of the risk that the forces under his command might repeat their previous conduct and unlawfully shell the OldTown.[1] The Trial Chamber characterised this risk as “a real and obvious prospect”, “a clear possibility”, “a risk that was not slight or remote”, and a “real risk”.[2] The Appeals Chamber moreover notes that the Trial Chamber found that the mens rea element of Article 7(3) of the Statute was not met before the commencement of the attack against Srđ because it found that it had not been established that Strugar “had reason to know that [unlawful shelling] would occur”,[3] that the risk of such shelling was shown “to have been so strong as to give rise, in the circumstances, to knowledge that his forces were about to commit an offence”[4] or that “there was a substantial likelihood of the artillery” unlawfully shelling the Old Town.[5] In addition, the Trial Chamber held that it was “not apparent that additional investigation before the attack could have put the Accused in any better position”.[6] The Appeals Chamber finally notes that the Trial Chamber found that Strugar’s notice, after the commencement of the attack against Srđ, of a “clear and strong risk”[7] or a “clear likelihood”[8] that his forces were repeating its previous conduct and unlawfully shelling the Old Town did however meet the mens rea requirement under Article 7(3).

304. Taking into consideration the relevant factual findings of the Trial Chamber, the Appeals Chamber finds that the Trial Chamber committed an error of law by not applying the correct legal standard regarding the mens rea element under Article 7(3) of the Statute. The Trial Chamber erred in finding that Strugar’s knowledge of the risk that his forces might unlawfully shell the Old Town was not sufficient to meet the mens rea element under Article 7(3) and that only knowledge of the “substantial likelihood” or the “clear and strong risk” that his forces would do so fulfilled this requirement. In so finding, the Trial Chamber erroneously read into the mens rea element of Article 7(3) the requirement that the superior be on notice of a strong risk that his subordinates would commit offences. In this respect, the Appeals Chamber recalls that under the correct legal standard, sufficiently alarming information putting a superior on notice of the risk that crimes might subsequently be carried out by his subordinates and justifying further inquiry is sufficient to hold a superior liable under Article 7(3) of the Statute.[9]

28. […] The “had reason to know” standard does not require that actual knowledge, either explicit or circumstantial, be established. Nor does it require that the Chamber be satisfied that the accused actually knew that crimes had been committed or were about to be committed. It merely requires that the Chamber be satisfied that the accused had “some general information in his possession, which would put him on notice of possible unlawful acts by his subordinates.”[1]

[…]

In paragraph 32, the Appeals Chamber observed that the Trial Chamber identified criminal negligence as a “third basis of liability.”

33. The Appeals Chamber wishes to recall and to concur with the Čelebići jurisprudence,[2] whereby a superior’s responsibility will be an issue only if the superior, whilst some general information was available to him which would put him on notice of possible unlawful acts by his subordinates, did not take the necessary and reasonable measures to prevent the acts or to punish the perpetrators thereof.

34. The Statute does not provide for criminal liability other than for those forms of participation stated therein, expressly or implicitly. In particular, it would be both unnecessary and unfair to hold an accused responsible under a head of responsibility which has not clearly been defined in international criminal law.

35. References to “negligence” in the context of superior responsibility are likely to lead to confusion of thought, as the Judgement of the Trial Chamber in the present case illustrates. The law imposes upon a superior a duty to prevent crimes which he knows or has reason to know were about to be committed, and to punish crimes which he knows or has reason to know had been committed, by subordinates over whom he has effective control. A military commander, or a civilian superior, may therefore be held responsible if he fails to discharge his duties as a superior either by deliberately failing to perform them or by culpably or wilfully disregarding them.[3]

36. Depending on the nature of the breach of duty (which must be a gross breach), and the gravity of the consequences thereof, breaches of duties imposed by the laws of war may entail a disciplinary rather than a criminal liability of a superior who is subject to military discipline. The line between those forms of responsibility which may engage the criminal responsibility of the superior under international law and those which may not can be drawn in the abstract only with difficulty, and the Appeals Chamber does not need to attempt to do so in the present Judgement.  It is better, however, that Trial Chambers do not describe superior responsibility in terms of negligence at all.

37. The Trial Chamber must be satisfied that, pursuant to Article 6(3) of the Statute, the accused either “knew” or “had reason to know”, whether such a state of knowledge is proved directly or circumstantially. The Appeals Chamber is of the opinion that the test for criminal negligence as advanced by the Trial Chamber cannot be the same as the “had reason to know” test in terms of Article 6(3) of the Statute. In the Appeals Chamber’s view, the Trial Chamber should not have considered this third form of responsibility, and, in this sense, it committed an error of law.

[…]

42. The Čelebići Appeal Judgement makes it clear that “a showing that a superior had some general information in his possession, which would put him on notice of possible unlawful acts by his subordinates would be sufficient to prove that he ‘had reason to know’.”[4] The Appeals Chamber endorses the finding of the ICTY Appeals Chamber in the Čelebići Appeal Judgement that the information does not need to provide specific details about unlawful acts committed or about to be committed by his subordinates.[5] […] [T]he Appeals Chamber, however, deems it necessary to make a distinction between the fact that the Accused had information about the general situation […] at the time, and the fact that he had in his possession general information which put him on notice that his subordinates might commit crimes. […]

238. […] A showing that a superior had some general information in his possession, which would put him on notice of possible unlawful acts by his subordinates would be sufficient to prove that he “had reason to know”. The ICRC Commentary (Additional Protocol I) refers to “reports addressed to (the superior), […] the tactical situation, the level of training and instruction of subordinate officers and their troops, and their character traits” as potentially constituting the information referred to in Article 86(2) of Additional Protocol I.[1] As to the form of the information available to him, it may be written or oral, and does not need to have the form of specific reports submitted pursuant to a monitoring system. This information does not need to provide specific information about unlawful acts committed or about to be committed. For instance, a military commander who has received information that some of the soldiers under his command have a violent or unstable character, or have been drinking prior to being sent on a mission, may be considered as having the required knowledge.

239. Finally, the relevant information only needs to have been provided or available to the superior, or in the Trial Chamber’s words, “in the possession of”.  It is not required that he actually acquainted himself with the information. In the Appeals Chamber’s view, an assessment of the mental element required by Article 7(3) of the Statute should be conducted in the specific circumstances of each case, taking into account the specific situation of the superior concerned at the time in question. Thus, as correctly held by the Trial Chamber,[2] as the element of knowledge has to be proved in this type of cases, command responsibility is not a form of strict liability. A superior may only be held liable for the acts of his subordinates if it is shown that he “knew or had reason to know” about them.  The Appeals Chamber would not describe superior responsibility as a vicarious liability doctrine, insofar as vicarious liability may suggest a form of strict imputed liability.

See also paragraphs 225-237.

30. While a superior’s knowledge of and failure to punish his subordinates’ past offences is insufficient, in itself, to conclude that the superior knew that similar future offences would be committed by the same group of subordinates, this may, depending on the circumstances of the case, nevertheless constitute sufficiently alarming information to justify further inquiry.[1] In making such an assessment, a Trial Chamber may take into account the failure by a superior to punish the crime in question. Such failure is indeed relevant to the determination of whether, in the circumstances of a case, a superior possessed information that was sufficiently alarming to put him on notice of the risk that similar crimes might subsequently be carried out by subordinates and justify further inquiry. In this regard, the Appeals Chamber stresses that a superior’s failure to punish a crime of which he has actual knowledge is likely to be understood by his subordinates at least as acceptance, if not encouragement, of such conduct with the effect of increasing the risk of new crimes being committed.

31. In the present case, the Trial Chamber, when it reviewed the Appeals Chamber’s application of the “had reason to know” standard in the Krnojelac case, found that “[o]ver and beyond the conclusions of the Appeals Chamber, the Chamber is of the opinion that by failing to take measures to punish crimes of which he has knowledge, the superior has reason to know that there is a real and reasonable risk those unlawful acts might recur”.[2] It further found that “by failing to punish, the superior (Krnojelac) did not prevent subsequent criminal acts”.[3] Those findings could be read as implying that a superior’s failure to punish a crime of which he has knowledge automatically constitutes sufficiently alarming information under the “had reason to know” standard, irrespective of the circumstances of the case. Such reading would amount to an error of law. However, the Trial Chamber also found that “from the moment a certain amount of information was available to Krnojelac which, taken as a whole, was sufficiently alarming and such as to alert him to the risk of murders being committed inside the prison, he had an obligation to intervene and at the least should have carried out an investigation”.[4] It also referred to the “had reason to know” standard as requiring an assessment of whether a superior had sufficiently alarming information which would have alerted him to the risk that crimes might be committed by his subordinates.[5] This demonstrates that the Trial Chamber correctly understood that standard as requiring an assessment, in the circumstances of each case, of whether a superior had sufficiently alarming information to put him on notice that crimes might be committed. […].

See also paras 267-268.