John Morton, DHS Memo Prosecutorial Discretion: Certain Victims, Witnesses and Plaintiffs (June 17 2011) [pdf]

This memorandum sets forth agency policy regarding the exercise of prosecutorial discretion in removal cases involving the victims and witnesses of crime, including domestic violence, and individuals involved in non-frivolous efforts related to the protection of their civil rights and
liberties. In these cases, ICE officers, special agents, and attorneys should exercise all appropriate prosecutorial discretion to minimize any effect that immigration enforcement may have on the willingness and ability of victims, witnesses, and plaintiffs to call police and pursue
justice. This memorandum builds on prior guidance on the handling of cases involving T and U visas and the exercise of prosecutorial discretion.