As has been mentioned throughout this Module, in addition to terrorism crimes established by the universal instruments against terrorism, which must be incorporated by States parties to them into domestic criminal legislation, it may be possible to prosecute some terrorist offences as core international crimes whether sourced in customary international law or codified within treaty texts such as the 1998 Rome Statute. Either way, however, since these crimes already exist in customary international law (Bassiouni, 1999, p. 522), nationals of States, which are not parties to particular treaties, can in theory still be prosecuted for their commission (consider the 1998 Rome Statute, article 98, and the United States Patriot Act (2001)).
The core international crimes of particular relevance here are crimes against humanity, war crimes and genocide. As recent discussions and debates regarding the heinous criminal acts of Islamic State and of how to bring those responsible to account illustrate, certain terrorist activities may cross the requisite legal threshold necessary to establish these most serious of international crimes. Similarly, the core international crimes apply to other terrorist groups too, such as Boko Haram which utilizes sexual violence as a means of terror, and is currently being investigated by the ICC for crimes against humanity and war crimes. (See International Criminal Court, Office of the Prosecutor, 2017, p. 46).
The essential elements of "crimes against humanity", as defined by article 7 of the Rome Statute, are that the specified prohibited acts are "committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack". The prohibited acts include crimes such as murder, extermination, inhumane acts, persecution, torture, rape, sexual slavery and enforced disappearance (article 7(2)), which commonly form the basis of terrorist acts. There is no single source that identifies the exact meaning of the key elements of a crime against humanity. Even the Elements of Crimes document of the International Criminal Court (2011), although it articulates the requisite elements for proving each of the crimes, does not define any terms, except quite minimally in the "Introduction" to article 7 and in footnotes. Further interpretative clarity has been developed through international jurisprudence, especially that of the ad hoc tribunals for former Yugoslavia and Rwanda.
There is no international treaty dedicated to crimes against humanity, as there is for war crimes and genocide. Although the jurisprudence has not always been consistent, the key elements are, namely, that the elements of "widespread" and "systematic" require a considerable element of seriousness (Security Council report S/25704, para. 48) resulting in a multiplicity of victims and "exclude isolated or random acts" ( Prosecutor v Tadić, 1997, para. 646). Of especial relevance to terrorism related offences, a crime may be "widespread" by the "cumulative effect of a series of inhumane acts or the singular effect of an inhumane act of extraordinary magnitude" ( Prosecutor v Blaskic, 2000, para. 206). One criterion though that some, but not all, terrorist attacks will be able to meet is the requirement that it is an organized, coordinated and not "random" attack, such as the 9/11 attacks committed by al Qaeda in 2001 or the Mumbai terrorist attacks perpetrated by Lashkar-e-Taiba in November 2008, for which there had been extensive planning and execution. Crimes against humanity originally were prosecutable only if committed during an armed conflict, but in recent years, a consensus has grown that they can be prosecuted whether committed during peacetime or in a context of armed conflict, and can technically only be committed against civilians though given the lack of a global convention on such crimes, the exact parameters of what this means in practice are not entirely or always clear. Certainly, many commentators believe that, e.g., the 9/11 terrorist attack would satisfy the necessary criteria to constitute a crime against humanity.
Unlike crimes against humanity, which may be perpetrated during both peacetime and times of armed conflict, war crimes must have a nexus to a situation of armed conflict. These crimes entail violations of international humanitarian law, such as deliberate or indiscriminate attacks against civilians, torture or cruel treatment of persons, and so forth.
Even if a situation of armed conflict exists, the structure, organization and modus operandi of at least most terrorist organizations are such that they would not constitute an "organized armed group" capable of being a party to an armed conflict, including a non-international armed conflict. An exception perhaps would be the Islamic State, which has been a party to the recent conflicts in Iraq and Syria, as an example. Evidence suggests that it is well structured, organized and resourced. In turn, Islamic State reportedly has no respect for and has violated many aspects of international humanitarian law, including Common article 3 to the 1949 Geneva Conventions, which article provides the bare minimum of humanitarian obligations during any armed conflict, through such activities as its widespread, deliberate attacks against civilians contrary to the principle of distinction, sexual violence and slavery, pillaging, torture, destruction of cultural property, and so forth. In so doing, they have utilized tactics and methods commonly associated with war crimes and terrorist acts - such as wilful killing and the extensive, intentional destruction of civilian property - together with terrorist acts and methods expressly prohibited under international humanitarian law (see Module 6) i.e. deliberate acts of terrorizing the civilian population. (See Geneva Convention IV relative to Civilians, article 33; Additional Protocol 1, article 51; and, Additional Protocol II, articles 4 and 13).
So far as the elements of inflicting terror against civilians are concerned, as with other forms of war crimes, the material element may take the form of attacks deliberately or recklessly directed towards the civilian population (i.e., not simply collateral damage, a degree of which is permissible under international humanitarian law as a reality of conflict), or else an attack which is indiscriminate or disproportionate. In terms of the mental element, the difficulty is that it is necessary to demonstrate "specific intent" discussed in this Module i.e., that the principal purpose of the criminal acts was to spread terror among the civilian population ( Prosecutor v Galić, 2006, para. 103-104). This can be difficult to prove due to the availability of a defence of collateral damage. Further, though the exact meaning of "terror" is unclear and debated, the International Criminal Tribunal for the former Yugoslavia has approached this as meaning that "extreme fear" of a certain intensity and duration are necessary ( Prosecutor v Galić, 2006, para. 137), or an "intentional deprivation of a sense of security" among those persons not involved in military activities ( Prosecutor v Dragomire Miloŝević, 2007, para. 886).
Although such terrorist acts are commonly omitted from international criminal instruments, including the Rome Statute and Statute of the International Criminal Tribunal for the former Yugoslavia - yet included in the founding Statutes of the International Criminal Tribunal for Rwanda and Special Court for Sierra Leone - tribunals have overcome this limitation in practice through their jurisprudence ( Prosecutor v Galić, 2006, paras. 97-105). The position now seems to be that the deliberate infliction of terror on a civilian population in a situation of armed conflict is a war crime contrary to both treaty and customary international law (Henckaerts and Doswald-Beck, 2005, pp. 8-11).
Amongst the core international crimes that might be perpetrated by terrorist actors are crimes against humanity and war crimes. Exceptionally though they may in theory fall into the category of genocide. Certainly, when the United Nations Independent International Commission of Inquiry on the Syrian Arab Republic published its findings in June 2016, it concluded that, in addition to multiple crimes against humanity and war crimes, the Islamic State of Iraq and the Levant (ISIL) had also committed acts of genocide against the Yazidis (Human Rights Council, Independent International Commission of Inquiry on the Syrian Arab Republic report A/HRC/32/CRP.2).
The objective material elements are specified in the 1948 Convention on the Prevention and Punishment of the Crime of Genocide (Genocide Convention) (article II), reflecting what is deemed customary international law and the basis of article 6 of the Rome Statute, as follows:
In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
(a) Killing members of the group;
(b) Causing serious bodily or mental harm to members of the group;
(c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
(d) Imposing measures intended to prevent births within the group;
(e) Forcibly transferring children of the group to another group.
Further clarity regarding the meaning of these elements has been given through the jurisprudence of the International Criminal Tribunal for Rwanda especially, including in the case of Akayesu. The term "killing" has been interpreted as "murder" i.e. voluntary or intentional killing ( The Prosecutor v Jean-Paul Akayesu, 1998, paras. 500-501). Although serious bodily or mental harm must have occurred, this "do[es] not necessarily mean that the harm is permanent and irremediable" ( The Prosecutor v Jean-Paul Akayesu, 1998, paras. 502-504), although it must be significant and not superficial in nature. Instead, "[i]t must involve harm that goes beyond temporary unhappiness, embarrassment or humilitation. It must be harm that results in a grave and long-term disadvantage to a person's ability to lead a normal and constructive life ... the Chamber holds that inhuman treatment, torture, rape, sexual abuse and deportation are among the acts which may cause serious bodily or mental injury." ( Prosecutor v. Radislav Krstić, 2001, para. 513). The harm may include acts of bodily or mental torture, sexual violence and persecution ( The Prosecutor v George Anderson Nderubumwe Rutaganda, 1999, para. 51). So far as "deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part" is concerned, this may take such form as "subjecting a group of people to a subsistence diet, systematic expulsion from homes and the reduction of essential medical services below minimum requirement[s]" ( The Prosecutor v Jean-Paul Akayesu, 1998, paras. 505-506) or the "deliberate deprivation of resources indispensable for survival, such as food or medical services" ( The Prosecutor v Clement Kayshema and Obed Ruzidana, 1999, para. 116). Notably too, measures intended to prevent births can take multiple forms -both physical and mental - not only sexual mutilation, sterilization, forced birth control, etc, but also rape intended to prevent births when the raped women subsequently refuse to procreate ( The Prosecutor v Jean-Paul Akayesu, 1998, paras. 507-508). Certainly, rape has been a recurring feature of Islamic State's and Boko Haram's criminal activities, which has sometimes resulted in death due to the resultant injuries. The forcible transfer of children is often accompanied by threats and intimidation ( The Prosecutor v Jean-Paul Akayesu, 1998, para. 509).
In terms of the extent of the act, in whole or part, this may take different forms. For example, the Trial Chamber in Kristic found that "the intent to eradicate a group within a limited geographical area such as the region of a country or even a municipality" could be characterized as genocide ( The Prosecutor v Jean-Paul Akayesu, 1998, para. 589).
With respect to the subjective mental element to establish genocide, this is provided for in article II(1) of the Genocide Convention (as well as in the corresponding customary rule), namely "intent to destroy, in whole or in part, a national, ethnical, racial or religious group". This type of intent constitutes dolus specialis i.e. an aggravated, special criminal intention is required in addition to the criminal intent to perpetrate the objective elements just described. This is specific and intentional in nature i.e. requiring more than recklessness or gross negligence. The International Criminal Tribunal for Rwanda defined "specific intent" as "the specific intention, required as a constitutive element of the crime, which demands that the perpetrator clearly seeks to produce the act charged" ( The Prosecutor v Jean-Paul Akayesu, 1998, para. 498). Specific intent can be inferred from a certain number of presumptions of fact, such as "from all acts or utterances of the accused, or from the general context in which other culpable acts were perpetrated systematically against the same group, regardless of whether such other acts were committed by the same perpetrator or even by other perpetrators" ( The Prosecutor v Jean-Paul Akayesu, 1998, paras. 523).
Although a difficult threshold to cross in order to meet the necessary material and mental elements, nevertheless it is technically possible for terrorist actors to cross this as ongoing debates regarding the possible commission of genocide against the Yazidis demonstrate.
As a final point, article III Genocide Convention expands on the criminal acts as follows:
The following acts shall be punishable:
(b) Conspiracy to commit genocide;
(c) Direct and public incitement to commit genocide;
(d) Attempt to commit genocide;
(e) Complicity in genocide.
The ICTY and ICTR Statutes mirror this extension of the crime. The 1998 Rome Statute does not.
Even where the material and mental elements of core international crimes may be satisfied, as with crimes sourced in the universal instruments against terrorism, there are many practical challenges associated with investigating and prosecuting terrorist actors for their commission of core international crimes, whether sourced in customary international law, an international treaty such as the 1948 Genocide Convention, or even a Security Council resolution, which formed the basis of the International Criminal Tribunal for former Yugoslavia and the International Criminal Tribunal for Rwanda founding Statutes (UNSC Resolution 827 (1993) and 955 (1994)).
One significant challenge remains physically apprehending alleged perpetrators, especially the leaders of terrorist groups in order to investigate and prosecute them. Another relates to the physical obstacles associated with evidence gathering, particularly in a conflict/post-conflict environment when much of it may be inaccessible, destroyed or sourced in sensitive intelligence. Where the perpetrators are foreign terrorist fighters, other difficulties that can arise include inadequate domestic criminal legislation to deal with this type of criminal and crime. As noted above, under the principle of "double (or dual) criminality", a suspect can usually only be extradited from one State (e.g., where the person is apprehended) to another State (to face prosecution) where the offence is largely the same within both States. At present, there is a significant gap in adequate domestic legislation in many parts of the world to deal with such foreign fighters in many parts of the world.