A previously unreleased trove of documents related to the Chicago police killing of a 17-year-old black teenager found that officers had lied about what they saw that night and destroyed evidence and changed witness statements.

The revelations appear to illustrate the depths of a sweeping cover-up that followed the 2014 shooting death and underline residents’ distrust of a police department that has long been mired in controversy and corruption.

Officer Jason Van Dyke, who is white, fired 16 shots into Laquan McDonald on 20 October, 2014. The killing was captured on an officer’s dashboard-mounted camera, and the court-ordered release of that footage a year later had contradicted officers’ statements with their version of events.

In his interviews with the police department and Independent Police Review Authority, Van Dyke made “numerous false statements and material omissions” which “all served to exaggerate the threat McDonald posed”, according to a host of documents from the Chicago Inspector General’s office released on Wednesday containing interviews with 16 officers involved with the shooting.

Van Dyke argued that McDonald rushed him with a “potentially deadly knife attack”, according to the report, but the dashboard video "puts a lie to Van Dyke’s narrative and proves it has little basis in reality”.

His version of events has “irrevocably tainted his credibility and has wholly disqualified himself” from serving the department, according to the report.

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McDonald’s death was among a streak of high-profile killings involving white police officers and black men - in many cases unarmed - leading to mass demonstrations and protests and galvanising a Black Lives Matter movement that challenged institutional racism and police relationships with black communities.

Last year, Van Dyke was sentenced to six years and nine months in prison after being found guilty of second-degree murder and 16 counts of battery with a firearm. He was the first Chicago police officer to be charged with first-degree murder for an on-duty killing in more than 30 years.

Documents released by new Chicago Mayor Lori Lightfoot’s administration collect officer interviews, statements and summary reports from a 2016 investigation by Chicago Inspector General Joseph Ferguson. The reports have largely remained hidden from the public but became a focus of Ms Lightfoot’s campaign and her subsequent request to Chicago’s City Council to give the mayor’s office authority to release sensitive documents with public interest.

In a statement, Ms Lightfoot said the release of the documents “represents the first of many steps we are taking to ensure our city operates with nothing short of the highest levels of transparency”.

The recently released documents also reveal the internal cover-up to support Van Dyke’s version of events.

Before he recreated his officers’ reports, Lt Anthony Wojcik had “improperly disposed” of three reports containing officers’ handwritten notes from witness statements and “purposefully destroyed evidence”, according to the inspector general’s office, which recommended Mr Wojcik be discharged. He retired in 2016.

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The inspector general’s office also concluded that Sgt Stephen Franko, who was fired for his role in the cover-up, had knowingly approved Van Dyke’s false statements to establish the department narrative.

The investigation also revealed that other officers had lied and said they had heard Van Dyke yelling for McDonald to drop a weapon, statements that “bolster a false narrative which might offer justification for the shooting”. Those officers would not have been able to hear Van Dyke from where they said they were standing, and four other officers failed to record what was happening, according to the report.