David Koschman, 21, died of brain injuries two weeks after he and a group of friends tangled with Daley nephew Richard Vanecko, then 29, and his friends in a drunken faceoff on April 25, 2004. Police say Vanecko punched Koschmann, who fell back and cracked his head on the pavement.
The police department's original case files disappeared at some point and were found only recently, a high-ranking source told the Chicago Sun-Times, whose inquiries prompted a new inquiry.
Detectives brought in to reopen the investigation were therefore working with incomplete records when they declared the case closed March 1, ruling that Vanecko, who now lives in California, delivered the fatal punch but should not be charged. A source said the new information gave no reason to change the decision.
Police officials would not give details on how long the files were lost or where and when they were found.