The United States Marshals Service, a division of the US Department of Justice, provides for the security, health and safety of government witnesses  and their immediate family whose lives are in danger because they are testifying in court against drug traffickers, terrorists, organized crime members and other major criminals.

To begin with, the United States Attorney General makes the final determination who qualifies for protection. After the witness agrees to enter the program, they and their family are immediately relocated to a different and more secure location selected by the Marshals Service, this is usually a different city in a different state. Witnesses and their families typically get new names and identities, with authentic documentation like Social Security cards and driver's licenses. Housing, medical care, job training and employment can also be provided. Money for living expenses is also provided to the witnesses until they become self-sufficient in the relocation area.

This information was taken from 'Witness Protection Program Factsheet' from the US Department of Justice US Marshals. More information is also available on the Witness Security Program from the US Marshals.