The City Council is looking to restrict New York City's cooperation with federal authorities in enforcing detainers, under which local law enforcement holds people it might otherwise release so immigration officials can come get them. The city's role in the detainer system is a long-standing concern of advocates, and some have expressed some frustration at the continuation of the policy under Mayor de Blasio.
A report on the Department of Corrections website provides a little detail on how the program operated in the October 2012 to September 2013 period, when just over 3,000 detainers were honored and 1,163 were not.
Of the 3,074 people handed over to the feds, several had criminal convictions or existing deportation orders against them. Others had warrants or faced felony or misdemeanor charges—of which, as the saying goes, they were presumed innocent. A few had names that popped up on government databases of gang members and terrorist suspects.
But about a third had none of those things against them. See the details here and check out the chart below: