Saul Chavez, 36, is accused of running over and killing 66-year-old William "Denny" McCann in his Northwest Side Logan Square neighborhood last year.
Chavez was released on bond and disappeared.
McCann's family believes Chavez would still be in custody if the Cook County board hadn't passed an ordinance that let the jail ignore an order by U.S. Immigration and Customs to detain Chavez after he posted bond.
Commissioners say these federal "detainers" are requests, not arrest warrants.