CHICAGO (CBS/AP) — A special prosecutor has released a report concluding there’s no evidence former Chicago Mayor Richard M. Daley or other family members sought to influence an investigation into the 2004 death of a man punched by Daley’s nephew.

Dan Webb released the 162-page document Tuesday.

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A statement accompanying the reports says “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.

Twenty-one-year-old David Koschman died days after being struck by Daley’s nephew, Richard J. Vanecko.

Vanecko pleaded guilty Friday to involuntary manslaughter, leading a judge to unseal the report.

After completing the report last year, Webb said charges related to the original investigation weren’t possible because the statute of limitations ran out. The report details several lapses in procedures surrounding the incident.

The special grand jury issued 160 subpoenas for documents and testimony and collected 300,000 pages of evidence, including telephone records, emails, police reports, medical records, backup drives, video surveillance and receipts.

The report said email records for the Chicago Police Department and State’s Attorney could not be recovered because they no longer existed due to record retention policies.

The report says “Vanecko hit Koschman with a flush head-on punch that hit Koschman square in the face.”

A witness says “Koschman came flying back and fell straight back like dead weight” when it hit the pavement.

The report says the detectives picked that day were the first two detectives in on shift, Rita O’Leary and Robert Clemens

O’Leary said she probably took notes while interviewing Vanecko’s friends. Clemens said he didn’t take any notes, according to the report.

General Progress Reports or GPRs are missing from O’Leary on the day she interviewed Vanecko’s friends on April 25, 2004. Former Police Supt. Jody Weiss testified that missing GPRs raise red flags about an investigation.

After initial incident, two detectives worked on the case for a single day. They were given a list of six witnesses to contact regarding statements.

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None were contacted until three days after Koschman died and 13 days after the initial incident, the report said.

According to the report, it was well known that O’Leary was leaving for extended leave but higher ups assigned her the Vanecko case anyway.

The report stated that the case should have been assigned to detectives who could work on it day after day.

The report’s release came after Vanecko, now 39 and living in Costa Mesa, Calif., pleaded guilty Friday to involuntary manslaughter in a plea deal. He’ll serve 60 days in jail, followed by 60 days of home confinement, and must pay $20,000 in restitution.

His plea agreement short-circuited the need for a trial, which had been scheduled to begin later this month, and it led a judge on Monday to order that Webb’s final 2013 report be unsealed.

Webb wrote that when re-examining the case’s handling, he primarily looked at whether one of four laws had been broken: official misconduct, obstructing justice, conspiracy, and tampering with public records. Because each has a three-year statute of limitations, none could have been applied to the handling of the original 2004 investigation, he wrote, also citing a lack of potentially vital evidence, including emails and cellphone records.

And while reopened investigations in 2011 and 2012 were not subject to the statute of limitations, the report concluded that charges couldn’t be filed against any of the investigators.

“The Special Prosecutor does not believe he could prove beyond a reasonable doubt by legally sufficient evidence at trial that any employee of (the Chicago police) or (prosecutor’s office) acted with the requisite criminal intent … to violate Illinois law,” it said.

Vanecko’s plea on Friday came as a surprise.

Judge Maureen McIntye accepted the plea and ordered Vanecko to apologize to Koschman’s mother, Nanci Koschman.

Vanecko said in court about her, “I cannot imagine the pain and suffering Mrs. Koschman has gone through.”

Nanci Koschman told the judge she felt at least some sense of justice, saying, “I have a little peace of mind. I know I got a little justice for David.”

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