Officer's dashcam microphone 'intentionally destroyed' before Laquan McDonald shooting
Laquan McDonald was shot 16 times by a Chicago police officer (Screenshot)

The microphone equipment for the dashboard camera in the cruiser in which Chicago police officer Jason Van Dyke was riding on the night he fatally shot 17-year-old Laquan McDonald had been “intentionally destroyed”, according to maintenance documents first acquired by DNAinfo .

Related: ‘Nothing happens to the police’: forced confessions go unpunished in Chicago

The records, which include service requests on hundreds of Chicago police vehicles, show that officers have routinely been involved in the intentional destruction and sabotage of body worn microphones that sync with dashboard camera video.

After the video of the Laquan McDonald shooting was released in November, it was discovered that as much as 80% of the department’s dashcam footage was missing audio. This was determined to be due to technical failure, human error or in some cases, according to police spokesman Anthony Guglielmi, “intentional destruction”.

William Calloway, a Chicago-based activist who was instrumental in obtaining the release of the Laquan McDonald footage, said the logs proved a premeditated effort by officers to avoid transparency.

“They are intentionally sabotaging this audio equipment because in their mind, they’re going to do something wrong or reckless when they’re outside on the beat,” Calloway said.

He added that he was “absolutely not shocked or surprised about it at all”.

The records show that the dashcam in Van Dyke’s vehicle, 6412, was repaired on 17 June 2014, about three months after it was reported broken. The next day, the system was reported broken again. What technicians called “intentional damage” was not repaired until 8 October 2014, DNAinfo reported.

On 20 October, the dashcam (and one in another car) recorded Van Dyke’s fatal shooting of McDonald. The next month, technicians noted the missing audio in the car’s footage and suggested “it is apparent from the uploaded videos that personnel have failed to sync the mics”.

In November 2015, after the video emerged, Van Dyke was charged with homicide .

At least six other vehicle records show technicians noting that officers had not synced their microphones. Thirty service records show cases where either mics were not synced correctly or had been “intentionally defeated”.

More than 100 records show systems missing microphones, or having damaged systems with missing components like batteries and antennas.

Before the files were released, in December, Fraternal Order of Police president Dean Angelo scoffed at the idea that officers were intentionally disabling units.

“If they’re claiming officers are purposely breaking things, then where is the history of that? Are [officers] being written up? Does the department have documentation to back those claims up? I’d like to see it,” Angelo told DNAinfo.

In December, the Chicago Sun-Times reported that before the McDonald video was released, some officers threw their microphones on to a station roof, apparently in protest about having to be recorded. A sergeant who saw the incident reported it to Chicago’s Independent Police Review Authority.

The Chicago police department owns a long legacy of misconduct that includes torture scandals concerning Commander John Burge and Detective Richard Zuley, and the operation of the Homan Square “black site”.

The most recent scandal, over an apparent attempt to cover up the Laquan McDonald shooting, has resulted in a US Department of Justice investigation. © Guardian News and Media 2016