SPRINGFIELD — In the latest stage of a litigious saga over a longtime Chicago police practice, the Illinois Supreme Court last week agreed to hear a case challenging the constitutionality of arresting people on the basis of so-called “investigative alerts” without warrants.  The case is one of 12 petitions for leave to appeal — seven criminal and five civil — accepted by the high court. In total, 192 petitions were submitted to the high court’s March docket. The court …