Realistically the scale of perpetration in Syria and Iraq is such that a minute fraction of perpetrators are ever going to be brought before a criminal court or tribunal. Ultimately alternative justice mechanisms of the sort to which you're referring are going to have to be put into place, such as truth commissions, or truth-seeking and truth-telling processes. We're criminal law people, as you'll have inferred, but we've built our evidential holdings and organized them in a way that ultimately they can be used by transitional justice mechanisms such as these.
On November 22nd, 2016. See this statement in context.