Garda chief who led Graham Dwyer murder case and IRA probes retires
The senior Garda officer who led the investigation that brought Graham Dwyer to justice retires this month after 40 years' exemplary service to the State.
Chief Superintendent Diarmuid O'Sullivan, who commands the Dublin Eastern Division, was the first investigator to unmask the Foxrock architect as the prime suspect in the murder of Elaine O'Hara.
During the marathon trial, it emerged that the senior officer and a colleague retrieved a number of items from a bin outside Dwyer's home in the dead of night in order to obtain a sample of his DNA.
In what became known as the "dumpster diving" episode during the Graham Dwyer investigation, it emerged that O'Sullivan had been secretly tipped off that Dwyer might be the suspect.
"It was an operation to confirm intelligence that I had received from a confidential source," he said.
But the successful conviction of one of the country's most notorious killers was just one of a long list of achievements that stand out in the Kerryman's 38-year career as a police officer.
A native of Cahirciveen who joined An Garda Síochána in 1977, O'Sullivan spent almost three decades in the Special Detective Unit (SDU) where he earned a reputation as one of the country's foremost counter-terrorism experts.
A student of counter-terrorism leadership at a number of universities including Harvard University, he worked closely with international intelligence agencies to snare Republican terrorists and arms dealers.
O'Sullivan was one of the lead investigators in the dramatic spy mission in which US undercover agent David Rupert was planted in the heart of the Real IRA, the Republican gang responsible for the Omagh bombing.
That operation led to the conviction of RIRA boss Michael McKevitt, who was jailed for 20 years on a charge of directing terrorism between August 1999 and October 2000.
During the trial Mr Rupert, who had been recruited by the FBI, revealed that McKevitt had plotted the assassination of Tony Blair.
O'Sullivan also played a pivotal role in the capture and conviction of several other senior members of the Real IRA and Continuity IRA, including the RIRA's so-called director of operations Liam Campbell and Alan Ryan, who was murdered in a gangland feud in 2012.
The efforts of the SDU - also known as the Special Branch - have been widely acknowledged as successfully keeping the dissident gangs at bay, with members being arrested at the rate of an average of 40 per year.
As part of his role as the senior operations officer of the Special Branch, O'Sullivan was one of those responsible for the establishment of the State's first Witness Protection Programme during the Veronica Guerin murder investigation in 1996.
He was also tasked with co-ordinating the huge security operations surrounding several high-profile State visits to Ireland including those of Queen Elizabeth and US Presidents Barack Obama and Bill Clinton.
In October, O'Sullivan launched a crackdown on serious crime in the north east of the country when he was seconded to head up the Louth Division following the vicious murder of Garda Tony Golden three months ago.
A local Garda source described how O'Sullivan had given officers in the division a "much-needed morale boost" during that time.
"O'Sullivan's background in combating terrorism meant that he understood what our members are up against along the border," he added.
Detective Superintendent Kevin Dolan, a close friend and colleague, described him last night as an "outstanding policeman".
"People like Diarmuid don't seek praise or glory for the work they have done but a lot of people are alive because of him," Det Supt Dolan said.
Hundreds of gardaí and civilians are expected to attend a function to mark his retirement tonight.