One of the major problems with undertaking prosecutions on the basis of universal jurisdiction is that the existence of jurisdiction per se does not give rise to any obligations on behalf of the territorial or nationality State to assist in any investigation, provide evidence or extradite suspects.
The matter of cooperation falls to treaty obligations or comity. It is perhaps unsurprising that some of the most successful prosecutions on the basis of universal jurisdiction, the Belgian prosecution of the ‘Butare four’, the Niyontenze case in Switzerland and the UK prosecutions of the Afghan warlord, Faryadi Zardad and Nazi war criminal Anthony Sawoniuk, occurred with the concurrence, if not the support, of the territorial States.
Those States permitted investigations and on-site visits, as well as providing witnesses to testify in the forum State. Although in some prosecutions on the basis of universal jurisdiction, witnesses are found in the forum State among the refugee community, the availability of evidence, both human and physical, cannot be presumed. A number of cases based on universal jurisdiction have failed to achieve the standard of proof for a criminal conviction.
Even where witnesses are available, problems of inter-cultural understanding can arise. Translation difficulties, as well as difficulties of appraising the credibility of witnesses testifying through interpretation and from different cultural backgrounds, make the appraisal of witness evidence very difficult. In some cases (the Sawoniuk case being an example), this problem is mitigated by on-site visits by the fact-finders, who can thereby achieve a better understanding of the witnesses’ cultural and material context.
There is also the possible problem of ‘forum shopping’, in which victims or NGOs may seek to initiate prosecutions in multiple fora, to maximize the possibility of a conviction. This can raise the important issue of the rights of defendants, who could be prosecuted (and have to defend themselves) repeatedly in relation to the same facts, something which, if done in one State, would violate the ne bis in idem principle.
The absence of such a principle operating between States makes this a possibility, albeit one which is not unique to
universal jurisdiction nor one which has occurred in practice.