ENDF forces have committed murder, torture and rape in the course of widespread and possibly systematic attacks directed against the Anuak civilian population in Gambella. Human Rights Watch believes that these attacks bear the hallmark of crimes against humanity under international law.
Crimes against humanity were first codified in the charter of the Nuremberg Tribunal of 1945. The purpose was to prohibit crimes which either by their magnitude and savagery or by their large number or by the fact that a similar pattern was applied endangered the international community or shocked the conscience of mankind.197 Since then, the concept has been incorporated into a number of international treaties and the statutes of international criminal tribunals, including the Rome Statute of the International Criminal Court.198 The definition of crimes against humanity varies slightly by treaty, but as a matter of customary international law the term crimes against humanity includes a range of serious human rights abuses committed as part of a widespread or systematic attack by a government or organization against a civilian population.199 Murder, torture and rape all fall within the range of acts that can qualify as crimes against humanity.200 Unlike war crimes, crimes against humanity may be committed in times of peace or in periods of unrest that do not rise to the level of an armed conflict.
Crimes against humanity include only abuses that take place as part of an attack against a civilian population. So long as the targeted population is of a predominantly civilian nature, the presence of some combatants does not alter its classification as a civilian population as a matter of law.201 Rather, it is necessary only that the civilian population be the primary object of the attack.202 Thus abuses ENDF forces directed against Anuak civilians even during the course of military operations in Anuak villages and neighborhoods can fall under the definition of crimes against humanity.
The attack against a civilian population underlying the commission of crimes against humanity must be widespread or systematic. It need not be both.203 Widespread refers to the scale of the acts or number of victims.204 Human Rights Watch considers the numerous acts of murder, torture and rape by ENDF soldiers against the Anuak civilian population to be widespread. Human Rights Watch documented more than 500 extrajudicial killings and dozens of incidents of rape and torture across nineteen different Anuak communities, starting with the December 2003 massacre in Gambella town and continuing throughout 2004. The December 2003 massacre, which claimed as many as 424 lives and resulted in the near-total destruction of the towns largest Anuak neighborhoods, can by itself be considered a widespread attack. Even a single violent attack that is part of broader widespread operation may amount to a crime against humanity.205
A systematic attack indicates a pattern or methodical plan.206 International courts have considered to what extent a systemic attack requires a policy or plan. For instance, such a plan need not be adopted formally as a policy of the state.207 Human Rights Watch does not have evidence allowing a conclusive determination one way or the other as to whether the abuses committed by ENDF forces in Gambella have been systematic. Nonetheless, the similarity of many of the attacks on the 19 neighborhoods, towns and villages in 2004 documented by Human Rights Watch strongly suggests a pattern to the attacks. While abuses were committed at different times and in different locations, they do not appear to have been a series of sporadic and unconnected events. 208
Finally, for persons to be found culpable for crimes against humanity requires their having the relevant knowledge of the crime.209 That is, perpetrators must be aware that their actions formed part of the widespread or systematic attack against the civilian population.210 While perpetrators need not be identified with a policy or plan underlying crimes against humanity, they must at least have knowingly taken the risk of participating in the policy or plan.211 An investigation into crimes against humanity in Gambella would need to address this element of the crime.
The Ethiopian government has a legal obligation to prosecute and punish officials and military personnel responsible for the commission of crimes against humanity.212 Those accused of crimes against humanity cannot avail themselves of the defense of following superior orders nor benefit from statutes of limitation. Because crimes against humanity are considered crimes of universal jurisdiction, all states are responsible for bringing to justice those who commit crimes against humanity. There is an emerging trend in international jurisprudence and standard setting that persons responsible for crimes against humanity, as well as other serious violations of human rights, should not be granted amnesty.
 History of the United Nations War Crimes Commission and the Development of the Laws of War (1943), p. 179, quoted in Rodney Dixon, Crimes against humanity, in Commentary on the Rome Statute of the International Criminal Court (O. Triffterer, ed.) (1999), p. 123.
 Rome Statute of the International Criminal Court, 2187 U.N.T.S. 3, entered into force July 1, 2002.
 See Rodney Dixon, Crimes against humanity, in Commentary on the Rome Statute of the International Criminal Court (O. Triffterer, ed.) (1999), p. 122. This is the standard applied by Article 7 of the Rome Statute of the International Criminal Court. Ethiopia is not a state party to the Rome Statute and is therefore not bound by it, but the definition in Article 7 accords with the conception of crimes against humanity in customary international law.
 Murder and torture are among the core offenses that have been included within the definition of crimes against humanity at least since the adoption of the charter establishing the Nuremberg tribunal after World War II. Rape was not explicitly included in the charters definition of crimes against humanity in article 6(c) although it could be derived from that definitions general prohibition against other inhumane acts. This ambiguity has been resolved in recent years; the statutes of the International Criminal Tribunals for Rwanda and the former Yugoslavia as well as the Rome Statute all explicitly include rape in the list of enumerated offenses that can constitute crimes against humanity. The ICC Statute also lists: extermination, enslavement, deportation, imprisonment, persecution, enforced disappearance, apartheid, and other inhumane acts. ICC Statute, article 7(1).
 See, e.g., Prosecutor v. Naletilic and Martinovic,International Criminal Tribunal for the former Yugoslavia (ICTY), Trial Chamber, March 31 2003, par. 235 (The population against whom the attack is directed is considered civilian if it is predominantly civilian); Prosecutor v. Akayesu, International Criminal Tribunal for Rwanda (ICTR), Trial Chamber, September 2, 1998, par. 582 (Where there are certain individuals within the civilian population who do not come within the definition of civilians, this does not deprive the population of its civilian character); Prosecutor v. Jelisic, ICTY Trial Chamber, December 14, 1999, par. 54 (The presence within the civilian population of individuals who do not come within the definition of civilians does not deprive the population of its civilian character.).
 See Naletilic and Martinovic, para. 235.
 See Prosecutor v. Tadic, ICTY Trial Chamber, para. 646 (it is now well established that the acts can occur on either a widespread basis or in a systematic manner. Either one of these is sufficient to exclude isolated or random acts.).
 Akayesu defined widespread as massive, frequent, large scale action, carried out collectively with considerable seriousness and directed against a multiplicity of victims, Prosecutor v. Akayesu, ICTR Trial Chamber, September 2, 1998, para. 579; see also Kordic and Cerkez, ICTY Trial Chamber, February 26, 2001, para. 179; Kayishema and Ruzindana, ICTR Trial Chamber, May 21, 1999, para. 123.
 See, e.g., Kordic and Cerkez, ICTY Trial Chamber, February 26, 2001, para. 178.
 Tadic, para. 648. In Kunarac, Kovac and Vokovic, the Appeals Chamber stated that patterns of crimesthat is the non-accidental repetition of similar criminal conduct on a regular basisare a common expression of [a] systematic occurrence. Para. 94.
 Akayesu, para. 580.
 See Blaskic, ICTY Trial Chamber, March 3, 2000, para. 204
 See Prosecutor v. Kupreskic et al., ICTY Judgment, January 14, 2000, para. 556.
 See Kupreskic et al., ICTY Trial Chamber, January 14, 2000, para. 556: [T]he requisite mens rea for crimes against humanity appears to be comprised by (1) the intent to commit the underlying offence, combined with (2) knowledge of the broader context in which that offence occurs. See also Tadic, ICTY Appeals Chamber, para. 271; Kayishema and Ruzindana, ICTR Trial Chamber, May 21, 1999, paras. 133-134.
 See Blaskic, ICTY Trial Chamber, March 3, 2000, para. 257. Blaskic (paras. 258-259) listed factors from which could be inferred knowledge of the context:
[a] the historical and political circumstances in which the acts of violence occurred; [b] the functions of the accused when the crimes were committed; [c] his responsibilities within the political or military hierarchy; [d] the direct and indirect relationship between the political and military hierarchy; [e] the scope and gravity of the acts perpetrated; [f] the nature of the crimes committed and the degree to which they are common knowledge.
 See, e.g., United Nations General Assembly Resolution 3074, Principles of international cooperation in the detention, arrest, extradition and punishment of persons guilty of war crimes and crimes against humanity, December 3, 1973. Under the Convention against Torture and Other Cruel, Inhuman and Degrading Treatment or Punishment, to which Ethiopia is a party, the same obligation applies with respect to individuals who have committed acts of torture, irrespective of whether such acts are also classified as crimes against humanity.