There was "no evidence" former Chicago Mayor Richard M. Daley tried to influence investigations into the 2004 death of a man who got into an altercation with Daley's nephew, a special prosecutor concluded in a report released today.

David Koschman died in 2004 after a drunken dispute with Daley's nephew, Richard "R.J." Vanecko.

But the report also asserts that Daley and members of his staff knew "shortly after the incident" of Vanecko's possible involvement, even though his name didn't show up in police reports until almost three weeks later.

The report was completed last year but remained under seal until today.

In the early morning hours of April 25, 2004, 21-year-old Koschman and a group of his friends got into an alcohol-fueled verbal confrontation with Vanecko, then 29, and his friends outside a popular strip of bars on Division Street, according to the report's account of the incident.

It ended with Koschman knocked out cold to the sidewalk and Vanecko fleeing the scene with one of his friends. The other two in Vanecko's group initially lied to police and said they didn't know the men who had run away from the scene, the report said.

Koschman never regained consciousness. He died 11 days later at Northwestern Memorial Hospital of brain injuries caused by blunt force trauma. His death was ruled a homicide.

Daley, who served six terms as mayor of Chicago, was interviewed by the office of the special prosecutor, as were several of his relatives and former staff members. The investigation, led by prominent Chicago attorney Dan Webb, first sought to determine if anyone should be charged with causing Koschman's death. Secondly, the inquiry sought to examine whether Vanecko's family ties impacted the course of the homicide investigation.

One the first point, the answer was yes. In December 2012, a grand jury returned an indictment of Vanecko, charging him with involuntary manslaughter for "recklessly performed acts which were likely to cause death or great bodily harm to another."

Last week, in a plea deal with prosecutors, Vanecko admitted to throwing a single punch that led to Koschman's death. In exchange for the plea, prosecutors agreed to a reduced sentence of 60 days in jail, followed by 60 days of home confinement and two and a half years of probation. Vanecko was also required to offer an in-court apology to Koschman's mother, which he did.

While the special prosecutor's report is unsparingly critical of the way cops handled the initial investigation of the case and a subsequent re-examination of the evidence in 2011, Webb stopped well short of assigning any political motive.

In a statement accompanying the report's release today, Webb said his team "concluded there was no evidence that former Mayor Daley, his family, or others at their direction engaged in conduct to influence or attempted to influence" the investigations.

Daley acknowledged in his interview that he learned of the incident "sometime" after it had occurred, but was unable to say exactly when. He also told investigators that he had made it clear to his staff and the public that "because he was Vanecko's uncle, he had recused himself from any involvement in the Koschman matter."

The authorities in 2004 declined to pursue charges against Vanecko. Dennis O'Brien, then an assistant state attorney who reviewed the evidence and declined to prosecute Vanecko, told a grand jury impaneled by Webb last year that the case was "nowhere near chargeable" because of conflicting witness statements and questions about who was the aggressor during the confrontation.

The case remained dormant for several years until reporters for the Chicago Sun-Times in 2011 filed a series of freedom of information requests, seeking documents from police and prosecutors.

Though the Sun-Times was initially thwarted in its document requests, a series of investigative reports by the paper revealed that Koschman case files were mysteriously missing from both the police and prosecutor's office, and that there were troubling inconsistencies between witness statements and the official accounts of the incident.

Those revelations and the aggressive pursuit by the Sun-Times soon led to a renewed examination of the evidence and, ultimately, to a different conclusion. This time, according to the special prosecutor's report, Vanecko was identified by police as the person who threw the punch at Koschman, causing his death.

But the case was still closed without charging Vanecko because the detectives and police commanders determined that Koschman was the aggressor and Vanecko acted in self-defense.

The special prosecutor's report is unrestrained in its criticism of that determination, alleging that the detectives and commanders involved in that decision had effectively manufactured a "phony self-defense determination" for Vanecko, even though he never gave any statement to police about his state of mind.

Webb's report indicates that he considered charging six police department personnel with criminal misconduct for their handling of the 2011 re-investigation, but ultimately concluded that insufficient direct evidence existed to conclude that any of them had broken the law.

Vanecko, who has since moved to California, will begin serving his jail sentence in Illinois later this month.