An immigration hold (also called a detainer) refers to when an undocumented or illegal immigrant who is already in jail is held after a criminal charge, often past the person's scheduled release date, for transfer to Immigration and Customs Enforcement (ICE). The hold lasts for 48 hours, during which time ICE is supposed to pick the person up. (If it doesn't, then technically you can argue for release, but doing so usually triggers ICE picking the person up anyway.)
Checking in on who is the police have put in jail and whether they are in valid immigration status is a common ICE strategy for apprehending undocumented persons. Even people with green cards (lawful permanent residence) can have immigration holds placed on them, if they committed the type of crime for which someone can be deported.
The placement of an immigration hold can be disappointing for friends and relatives. Just when you thought the person was going to get out of jail or prison, he or she is transferred to an Immigration Custom Enforcement (ICE) detention center. These detention centers are separate from ordinary jails, and often located in distant locations; sometimes in other states from where the non-citizen has been living.
A person held by ICE ordinarily has a right to have their immigration case heard before an immigration judge. There's an exception, however, if an order of removal (deportation) is already outstanding against the person. In that case, the non-citizen likely has no right to any further hearings, and will be deported from the United States soon.
Assuming the non-citizen isn't deported from the U.S. right away as described above, the first hearing before an immigration court judge will be a short one. The purpose is to set a bond amount for release while awaiting the next hearing.
The next court hearing will fully cover the merits of the person's case. With the help of a lawyer, your family member might be able to argue against removal. For example, it might be possible to show the judge that your family member actually has a right to a green card or, if he or she already has a green card, that the crime committed is not actually enough to make a person deportable.
The hearings will be scheduled automatically, unless your family member makes the mistake of signing a document agreeing to be voluntarily removed from the United States. For more detail on the process, see The Immigration Hold Process After Jail.
If someone you know has been detained after an immigration hold, the first thing to do is to find out, if possible, which detention center the person has been transferred to. ICE's online detainee locator can help with this, but you'll need personal information, and the system isn't entirely reliable.
If your relative calls you, ask for details. Also advise him or her not to sign anything until you have gotten an attorney to consult with you.
Be warned: Transfer between detention facilities is not uncommon. Even after you figure out where your family member is today, he or she could be moved to another facility tomorrow, with little warning.
Consult an immigration attorney as soon as possible, preferably as soon as your relative is arrested. Agreeing to a guilty plea to avoid jail time can backfire if it leads to deportation. In fact, look for an attorney who has a subspecialty in how the immigration laws treat criminal matters. The attorney can help you figure out which facility your relative is being held at (though doing this can even be challenging for attorneys) and prepare a defense against any upcoming removal proceedings.