A number of practical steps can address these challenges. It is important for the prosecutorial strategy to be transparent. The decisions on what crimes and which alleged perpetrators are likely to be investigated must be made clear in order to maintain the integrity of the process. Two steps are essential: •A  mapping exercise should be carried out before developing a detailed prosecutorial strategy, taking into account the universe of suspects and victims; and • Provision should be made for outreach to explain the purposes of the prosecution policies and strategies. 1. Mapping A mapping exercise can assist preparation of prosecutorial initiatives by providing a sense of what kinds of crimes occurred, when and where, who the victims were, and the likely identity of the perpetrators.12 A mapping process could rely on detailed or official investigations, including those of international commissions of inquiry that have already taken place. The information to be gathered at this stage must meet only a prima facie standard. The objective is to provide the basis for the formulation of initial hypotheses of investigation by giving a sense of the scale of violations, detecting patterns and identifying potential leads or sources of evidence.13 Appropriate use of journalistic and civil society sources will often establish an adequate basis for setting out the broad trends of violations. The mapping process should be a preliminary exercise, carried out by a qualified team, and need not be prolonged. Its benefit is threefold: 1. It makes the process more objective by basing strategic decisions on preliminary indications of actual events, rather than on pure suppositions. 2. A  s a result of the former, it establishes the essential discipline of “rational hypotheses” in complex investigations, i.e., proceeding on the basis of presumptions which are supported by the facts and gradually building on those to construct further “hypotheses”. 3. It allows those directing the process to make more realistic estimates of the necessary resources. 12 In some circumstances, prosecutors have been able to take advantage of particularly detailed or sophisticated inquiries that made the determination of the universe of cases and formulation of initial hypotheses. For example, the work of the National Commission on Disappeared Persons in Argentina was extremely useful to prosecutions and is perhaps the best example of the effective use of existing material to frame an investigative strategy. In that case, an investigation that accounted for abuses of more than 9000 civilians led to 700 incidents being presented in criminal trials. However, a cautionary lesson may be learned from relying too much on previous reports, which may unnecessarily restrict the focus of the investigative efforts. Another example of this can be seen in the Special Prosecutor’s Office in Mexico, where the universe of cases in relation to several decades of abuses has been limited almost exclusively to matters already investigated by the National Human Rights Commission in relation to alleged disappearances and two other massacres subject to previous investigations. Many local NGOs have complained that insufficient attention has been paid to other credible information in relation to systematic abuses. 13  methodology on mapping will need to refrain from using methods that may be deemed to taint evidence, thus rendering it A useless for subsequent trials. This is a particular consideration for common-law jurisdictions, where technical rules of evidence may apply. For example, those carrying out the mapping should be cautious about taking statements from witnesses where these are likely to be subject to subsequent disclosure and likely to be used to attack witness credibility. Guidelines dealing with such considerations should be developed before embarking on the mapping.