No criminal justice system can be regarded as credible or effective, or as a deterrent to further offending, or a vehicle for vicarious revenge by the public, unless it is able to round up those it believes are guilty of crimes and put them on trial. Indeed, a criminal justice system that cannot do these things is scarcely worthy of the name. In most Western societies, arresting wanted criminals, if not always easy, is at least straightforward. Western police forces work in organized societies in which information about citizens is freely available. They can usually rely on the help of the public and, in serious cases, on the public taking the initiative to contact the authorities. They can usually count on the support of other government departments and even other governments. Most criminals in the West submit fairly quietly, and even dangerous and violent criminals can usually be arrested at a time when they are inattentive, unarmed, or asleep. Even in the United States, armed shootouts between police and criminals are not common, and there are few cases in which the criminals have more firepower than the police.
With occasional exceptions, the above scarcely applies to fugitives from international justice. To begin with, it may not be obvious who to look for. Almost by definition, war crimes take place in circumstances of confusion and dislocation. In some cases, targets for investigation and arrest may have official positions, and if investigators can get to official files, some details may be available. But even then, investigators may have no better idea who to look for. Consider the following hypothetical description of a