In a way, the question is at least a little bit circular: the "intent" provision of the Genocide Convention is most often interpreted as meaning that there cannot be a genocide without a policy. But there are two problems that immediately come forward here:
1) Even where a policy exists, it is very rare that this policy is stated in a conventional way that allows for documentation. The documentation of the Wannsee Conference (1942), for example, while it is usually taken as evidence of the announcement by the Nazis of the "Final Solution," is in fact vague on the question of what, other than deportation, this "solution" would entail (and its report was not a published document). Even the centrality of the Wannsee Conference is disputed: Christian Gerlach, for example, argues that a recently found document is more determinative and sets an earlier date. I am not about to resolve this historians' dispute -- what I want to point out out is that the dispute indicates a problem, which is that decisions to commit genocide do not lend themselves to documentation and publicity. The Nazi case takes place in the context of a regime which was sure of its power at the time and held closely to bureaucratic form, conditions which do not apply to the states of the former Yugoslavia. Even in Rwanda, where there is plentiful evidence of intent, this evidence takes the form of media material. There are no parliamentary resolutions or (written) executive decrees. So any evidence related to the existence of a policy has to be indirect.
2) To the extent that a policy can be said to have existed, there remains the question of whose policy it was. In the strictest bureaucratic sense, Serbia and the Serb parastate in Bosnia-Hercegovina were separate entities. To further complicate the matter, many of the worst atrocities were carried out by paramilitary groups (White Eagles, Tigers, Scorpions, and other critters) which had no legal status. The core of the case presented by the BiH advocates lies in demonstrating the ways in which all of these elements were connected. These are all facts that, in the parlance, "everybody knows," but that sort of qualification does not necessarily reach the required standard of legal proof. Alain Pellet of the BiH legal team himself raised the possibility that SRJ may have been "merely" an accomplice rather than a direct participant with intent in the genocide. But he raised this possibility more or less as a null hypothesis, in the process of attempting to show that the military and police forces of RS were "totally dependent on SRJ and have to be considered as organs of SRJ." Here, too, the evidence has to be indirect: the strategy depends on showing logistical, command and financial links between SRJ institutions and perpetrators.
Demonstrating links was the central concern of BiH attorney Magda Karagianakis, who spoke of the role of the Serbian interior ministry in training, arming and commanding the RS military (VRS) and paramilitaries. One well known example was broadcast to great publicity last year: the video recording showing prisoners who had been taken by the military being executed by members of a paramiltary unit. In addition to evidence from the plaintiffs' attorneys showing that VRS was financed directly by the regime in Belgrade, there remains Slobodan Milošević's interesting complaint at the time of his initial arrest, in which he denied that he had taken money missing from the state budget for personal or party use, claiming instead:
"As for the resources spent for weapons, ammunition and other needs of the Army of Republika Srpska and of Republika Srpske Krajine, those tasks for reasons of state, as a state secret, could not be shown in the budget, which is a public document. The same applies to appropriations for the supply of security forces, and especially the special antiterrorist forces --"from needles to locomotives" -- from light weaponry and equipment to helicopters and other resources which remain in place, and which were not revealed to the public for reasons of state secrecy."Similarly, the ongoing financial relations between the legal military and Ratko Mladić raises the issue of how close the informal contacts between institutions were, as do more recent revelations of the connections between state security and paramilitary groups. These sorts of statements and findings do not offer a high level of precision, but a lot of them cumulatively contribute to an argument that a variety of forces operated with a shared goal, and with some level of coordination.
The defence has a number of potential answers to arguments along these lines. One would be that in a war atmosphere characterised by general criminality and confusion, chains of command did not function (a similar argument is offered by Kosta Čavoški on behalf of Radovan Karadžić, but it will not help in this case -- he tries to shift blame to Milošević by way of Mladić). Another would be that the interior ministry and its forces represented rogue elements not controlled by state policy, but this argument faces the problem of finding more rogue than nonrogue elements as it develops the theory. On his first day of presentation, SCG advocate Radoslav Stojanović argued for a separation between the actions of the Milošević regime and the interests of the state and its citizens. This argument may have considerable political validity but it is not clear that it can translate to a legal argument.
My assessment would be that if ICJ finds that genocide took place, it will be hard for them not to find also that there existed a policy in which SRJ was engaged.