[3] Callinan quickly rose through the ranks of the organisation; he mainly served in Dublin, but he also spent had spells stationed in Waterford and County Mayo.
In the early 1990s, he was appointed as head of the "Tango Squad", a group of Gardai who spent the large majority of their on-duty time monitoring the activities of Martin Cahill, a notorious Irish mob boss.
The Tango Squad proved to be successful in thwarting many of Cahill's activities and preventing him from taking on any major criminal objectives; this helped boost Callinan's career significantly.
Fachtna Murphy resigned as Garda Commissioner in late 2010; Martin Callinan, who by this time was an extremely well versed guard and had taken part in almost all areas of the force, was one of the top choices for the job.
Reports from the Garda Síochána Ombudsman Commission, also known as GSOC, criticized the handling of Kieran Boylan, an informant to the Gardai about various drug trafficking cartels in Ireland.
His time as Commissioner was further damaged by revelations of botched investigation procedures in regards to the murder of Sophie Toscan du Plantier in 1996.
The Charleton Tribunal prompted the government to begin discussions about reviewing the money spent and advice was sought from the Attorney General on the legality of the matter.
[9] Callinan's resignation coincided with the outbreak of two other scandals; allegations that the Garda Síochána Ombudsman Commission (GSOC) was under surveillance by an unknown group which had used "government-level technology" following a counter-surveillance operation undertaken by a British private security firm, and the emergence that phone calls in Garda stations throughout the country had been recorded on a mass scale for over 30 years before the practice was brought to an end.