The Department of Justice makes the decision to approve or deny a proposed transfer based on your entire record. The Department of Justice considers the seriousness of the offense and your role in it, the existence of outstanding fines or restitution orders, your prior criminal record (if any), the strength of your ties to each country, and the likelihood that the transfer will promote your rehabilitation. Sometimes the government also considers special humanitarian concerns, such as terminal illness of you or a close family member. Before making a decision, the Department of Justice collects information from many places about each person seeking a transfer. The process usually takes at least 3 months.
For more information, visit the website of the Department of Justice, Criminal Division, Office of Enforcement Operations, International Prisoner Transfer Program.