The general rule is that a noncitizen cannot be removed until the sentence has been served. INA 241(a)(4)(A). The exception to this rule applies to certain nonviolent offenders. INA 241(a)(4)(B).
The immigration laws, 8 U.S.C. 1231(a)(4)(B), allow removal of certain nonviolent offenders prior to completion of a sentence of imprisonment. The International Prisoner Transfer Unit at DOJ processes applications for transfer, and examines several factors.If the client is in State custody, as opposed to federal, an additional layer of approval is needed. The first issue is whether or not the particular state participates in this program. Most states, but not all, have passed the statutes necessary to allow inmates from that state to participate in the transfer program. If the particular state has passed this legislation, the client should be informed of this option by the prison authorities upon entering the prison system.
Second, the government will get feedback from the law enforcement official involved in investigating the case and from the prosecutor's office. This is usually a sticking point. Law enforcement typically did not care where the person served the time. The prosecutors were another story. They almost always had objections based on the fact that once the person transfers they are no longer under their jurisdiction and are then subject to the laws of the country to which they are transferred. They typically fear that once the person is transferred they will just get be released without serving the time.
The applicant must also to have good behavior in prison. Any black marks as far as behavior will be a negative factor. Other factors include the nature of the offense, the length of the sentence, the amount of time already served, family ties in home country, and family ties in the United States. If the client is in state custody, the state (typically, the governor's office) will have to approve the transfer. Then the federal authorities can approve the transfer. Then the receiving country will have to accept the transfer.
If the client receives a fairly lengthy sentence, it is less likely he will receive a quick transfer. The government would probably prefer he serve some of his time here in the United States, unless the inmate has strong humanitarian factors in his favor.
If the client is a Lawful Permanent Resident, he will have to give up his rights to remain in the country and not fight deportation. If this is not done, there will be no transfer. Thanks to Jeanne Brennan Funk.