There has been a call for a technological recreation of a former garda chief’s vital missing mobile phone part to test allegations that he was part of a smear campaign against whistleblowers in his force.

Labour Party leader Brendan Howlin said investigators should be able to re-create former Garda Commissioner Martin Callinan’s missing SIM card, the unit that retains details in a mobile phone.

The card was never accessed by a commission that last year reported on the circumstances in which Callinan vacated his post and was succeeded on government appointment by his deputy Noirin O’Sullivan.

Howlin claimed the work of the commission headed by Justice Niall Fennelly was compromised by being unable to access the missing SIM card.

Now the government has appointed Justice Iarfhlaith O’Neill to examine new allegations of a smear campaign against whistleblowers attempting to expose corruption in the force.

Howlin emphasised the fact that Callinan’s SIM card was not available to last year’s commission did not incriminate him, but it was a worry if it was not available to the new inquiry when the details on it could be eliminated if necessary.

“There’s unanswered questions hanging and that’s very unsatisfactory. There’s nobody better placed than An Garda Síochána themselves to recreate a lost SIM. I think there are probably forensic mechanisms to re-check any communications. But I say that without making any allegations,” Howlin told The Irish Times.

O’Neill was appointed to examine two new protected disclosures made to Minister for Justice Frances Fitzgerald in the last two weeks. Both allege a smear campaign against Sergeant Maurice McCabe, a widely-recognized whistleblower who has exposed corruption.

In one of the disclosures, former head of the garda press office, Superintendent Dave Taylor, has alleged the existence of texts sent from garda headquarters with the aim of smearing McCabe.

Taylor has been suspended from work since last year and is being investigated for leaking information to the media.  He has said he was part of the smear campaign, but has insisted he was acting on orders.

References in reports of McCabe’s treatment cover the period when Callinan was garda commissioner up to March 2014, and afterwards when O’Sullivan was leading the force.

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