The Cook County state attorney's office said there isn't enough evidence to prosecute Richard J. "R.J." Venecko in the seven-year-old case even though the medical examiner said David Koschman, 21, died as the result of a homicide, the Chicago Tribune reported.
A prominent criminal defense attorney disagreed with the decision by Cook County State's Attorney Anita Alvarez not to prosecute Venecko, who is also the nephew of White House Chief of Staff William Daley.
"It seems to me there's a real possibility of a massive police cover-up here," said attorney G. Flint Taylor. "If this person were a normal citizen, particularly an African-American person and not the nephew of the mayor of Chicago, he would have been indicted on a variety of charges -- if not murder, involuntary manslaughter.
"Maybe there needs to be a special prosecutor," Taylor said.
Police determined Venecko punched Koschman, who fell and struck his head on the pavement. He later died from brain injuries.
Alvarez said in a statement the case would be difficult to prove because five witnesses have changed their stories since the incident occurred.
Additionally, the state attorney's office's files on the case have disappeared, Alvarez's staff said.