Callinan's papers were shredded and SIM removed from mobile
Personal papers belonging to the former Garda Commissioner were put into a number of black refuse sacks and subsequently shredded.
The Fennelly Commission also found the SIM card in Martin Callinan's phone was removed and never returned to Garda HQ.
It said it was striking how little documentary evidence is available for its investigation. Important decisions were not formally recorded, and were communicated orally, making it very difficult to identify what decisions were made, by whom, and for what reasons.
Mr Callinan told the commission he had cleared out all personal papers after he announced his retirement, and he did not have any written notes to support his evidence, particularly in relation to informing Brian Purcell, former secretary general of the Department of Justice, about the issue of the telephone recordings.
He was able to produce his diary for the year 2014.
On March 25, Mr Callinan went to a filing unit in the conference room, where he kept personal papers, and requested black refuse sacks, as he wished to sort through his files.
He later asked a Superintendent Walsh to dispose of eight to 10 bags of personal papers, which were shredded on April 4, 2014. His mobile was cancelled on May 30.
The report details how the SIM card in Mr Callinan's phone was removed before his phone was handed back to Garda HQ.
The commission queried the whereabouts of the phone, because evidence received showed almost all communication with the Department of Justice was by way of texts.
Mr Callinan said the phone he used as commissioner was an official phone and he did not know its whereabouts.
Assistant Commissioner Jack Nolan said that the phone had been returned to the force by Mr Callinan - but that the SIM card had been removed.
The Assistant Commissioner said he believed that the SIM card was subsequently destroyed.