In paragraph 13 the judges raise the issue of the perpetrators' access to the victims: "The historical examples of genocide also suggest that the area of the perpetrators’ activity and control, as well as the possible extent of their reach, should be considered. ... The intent to destroy formed by a perpetrator of genocide will always be limited by the opportunity presented to him. While this factor alone will not indicate whether the targeted group is substantial, it can—in combination with other factors—inform the analysis."
The issue of what is raised by judges in Paragraph 13?  What is the basis for suggesting that several factors regarding the activity of the perpetrators be considered?  The extent of what by the perpetrators was considered in an examination of their activity and level of control? What will always be restricted in terms of a perpetrator's intent to destroy? While the factor cannot independently indicate if the targeted group is substantial, it can do what?