The Sunday Tribune has learned that former superintendent Joe Shelly received the discretionary once-off payment from the Department of Justice when he took early retirement from the force last July, despite having been severely criticised at the Morris tribunal, which probed garda misdeeds in Donegal.

Retired judge Robert Barr, who headed the probe into John Carthy's killing, last week described Shelly's failure to properly interview Carthy's doctor as "extraordinary". Barr said there was "credibility" to the theory that Shelly decided "not to go down that road" to ensure that embarrassing assault allegations made by Carthy against gardai would not be publicly revealed at a later stage. He nominated Shelly as one of three officers who contributed to Carthy's death. Last year, John Carthy's sister, Marie, strongly criticised the garda commissioner for accepting the retirement of Shelly, saying it was an "absolute disgrace" that he could retire on full pension even though the Barr tribunal had yet to report.

Shelly, a 54-year-old father of three, is the only member of the force to have been investigated by the three Oireachtas tribunals established to probe alleged garda misdeeds since the foundation of the state. In addition to his role at Abbeylara, Shelly was a member of the 'murder squad' involved in the Kerry babies scandal, which culminated in the public tribunal headed by judge Kevin Lynch.

He was stationed in Letterkenny during the probe into the death of cattle dealer Richie Barron on 14 October, 1996, and was one of the officers involved in the controversial investigation into the McBrearty family in Co Donegal.

In the subsequent tribunal into events in Donegal, Justice Frederick Morris said that the garda investigation into Barron's death was "prejudiced, tendentious and utterly negligent in the highest degree".

Morris named Shelly, who was at the rank of detective superintendent while in Donegal, along with three other senior gardai, as all sharing "various degrees [of ] the burden or fault for this matter".

John Carthy was shot dead by members of the Garda Emergency Response Unit (ERU) when he emerged from his house carrying a loaded shotgun at around 6pm in the second day of the Abbeylara siege in April 2000. Shelly and the other scene commander failed to anticipate the possibility that Carthy might exit the property and were caught totally by surprise, the Barr report said.

"The greatest garda mistake at Abbeylara was not preparing for an uncontrolled exit by Mr Carthy from his housef Shelly, the scene commander, was one of those exposed to potential danger and had to run for cover, " it said.