David Koschman's mother is seeking court permission to sue the Chicago Police Department and prosecutors.
Mayor Daley's nephew, Richard Vanecko, fatally punched Koschman in 2004.
Vanecko was convicted in January, and served two months for involuntary manslaughter.
Koschman's mother said the phony police version of the fight portrayed her son as the aggressor to protect Vanecko.
Lawyers for the city and Cook County want Koschman's lawsuit dismissed.