Some incidents involving the Garda have attracted wide scale attention—such as those that led to the Morris and Barr Tribunals—and have resulted in broad reform initiatives. Other reports suggest that people who frequent gay and lesbian establishments feel that the Gardaí are not doing enough to tackle reported homophobic crime in Ireland. In 2007 there was also some debate when a potential Sikh applicant of the Garda Reserve requested that he be allowed wear a turban in place of a standard uniform cap - Ultimately the provision was not made as it was stated that the force had the same uniform requirements for all members.
The Kerry Babies case was one of the first public inquiries into mishandling of a Garda investigation. Later, in the 1980s, the Ferns Report (an inquiry into allegations of clerical sexual abuse) described as "wholly inadequate" the handling of one of eight formal complaints made to Wexford gardaí, but noted that the remaining formal complaints were handled in an "effective, professional and sensitive" manner.
The Gardaí were also criticised in the Murphy Report in relation to the handing over of the case of Fr. Edmondus (a pseudonym) to Archbishop McQuaid by Commissioner Costigan. Some very senior Gardaí were criticised for regarding priests as being outside their remit in 1960. On November 26, 2009, then Commissioner Fachtna Murphy apologised for the failure of An Garda Siochána to protect victims of child abuse in the Dublin Archdiocese. He said that inappropriate relationships and contacts between gardaí and the Dublin Archdiocese had taken place at a time of undue or misguided deference to religious authorities and that these were incompatible with any investigation. On 27 November 2009 he announced that a senior investigator would examine the findings in the report.
The Gardaí were criticised by the commission of investigation into the Dean Lyons case for their handling of the investigation into the Grangegorman killings. In his report, George Birmingham said that the Gardaí had used leading questions in their interviews with Lyons, and had failed to act on a suspicion that Lyons' confession was unreliable. For a period, the gardaí involved in the case failed to act on the knowledge that another man, Mark Nash, had confessed to the crime. They were also criticised for failing to keep adequate records of their interviews with Lyons.
In the 1990s and early 2000s there were a series of allegations, including suggestions of corrupt and dishonest policing in County Donegal. This became the subject of a judicial inquiry: the Morris Tribunal. The tribunal found that some gardaí based in County Donegal had invented a Provisional IRA informer, made bombs and claimed credit for locating them, and attempted to frame Raphoe publican Frank McBrearty Junior for murder– the latter case involving a €1.5m settlement with the State. In a report to the Minister for Justice, Equality and Law Reform the Morris Tribunal expressed grave concern about "organised insubordination" within the force that "proper discipline has been lost from Garda", suggesting that a few mischief-makers abused their positions within the Garda and used the disciplinary process to damage the force. The tribunal also expressed concern that recruits were brought into an undisciplined culture that had the potential to do great damage in the longer term, and warned that a "terrible and costly" waste of talent would occur if the situation continued. These scandals damaged the reputation and standing of the force in County Donegal.
On 20 April 2000, members of the Emergency Response Unit shot dead, from behind, 27-year-old John Carthy at the end of a 25-hour siege as he left his home in Abbeylara, County Longford with a loaded shotgun in his hands. There were allegations made of inappropriate handling of the situation and of the overuse of armed force by the Gardaí. This led to a Garda inquiry, and later a Tribunal of Inquiry chaired by Mr Justice Robert Barr. This inquiry was established on 1 July 2002, and the hearing of evidence was completed on 7 December 2004. The final report was expected within six months, but publication of the report was delayed until 20 July 2006. The official findings of the tribunal were that Sgt Michael Jackson made 14 mistakes in his role as negotiator during the siege, and that he failed to make real efforts to achieve resolution during the armed stand-off. It further stated however that Sgt Jackson was limited by lack of experience and resources ("psychologists, solicitors, dogs"). The tribunal recommended that there be an urgent review of Garda command structures, and that the ERU be with stun guns and other non-lethal options, including "non-compliant firearms support police dogs".
The Barr tribunal also recommended a formal working arrangement between Gardaí and State psychologists, and improvements in Garda training (especially for the ERU in siege situations, including those with mental illness as a factor). This included a recommendation that local Garda superintendents undergo refresher training for one week every year as scene commanders and a similar refresher course for ERU officers of the rank of inspector or superintendent. Garda Commissioner Conroy, in a letter to the family of John Carthy, stated that the force was 'truly apologetic' for his death. Former Superintendent Joe Shelley, whose failure to interview John Carthy was cited in the Barr Tribunal Report as "extraordinary", and who was also severely criticised in the Report of the Morris Tribunal into the controversial death of Richie Barron, was awarded a top-up bonus of €110,000 when he took early retirement in July 2005. Mr Justice Morris described Shelley's probe as ""prejudiced, tendentious, utterly negligent in the highest degree"".
One of the first charges of serious misconduct against the force came from the handling of the Sallins Train Robbery in 1976. This case eventually led to a serious miscarriage of justice and accusations that a "Heavy Gang" within the force intimidated and tortured accused. This eventually led to a Presidential pardon for one of the accused.
In 2004, an RTÉ "Prime Time" documentary accused elements within the Garda of abusing their powers by physically assaulting people arrested. A retired Circuit Court judge (W. A. Murphy) suggested that some members of the force had committed perjury in criminal trials before him but later stated that he was misquoted, while a Minister of State (Dick Roche, a junior government minister) accused Gardaí in one instance of "torture". The Garda Commissioner accused the television programme of lacking balance.
The Prime Time documentary followed footage published by the Independent Media Centre Ireland showing scuffles between Gardaí and Reclaim the Streets demonstrators. One Garda in this footage was later convicted of common assault, which is a summary matter, while several other Gardaí were acquitted.
The family of Eddie Fullerton, a Buncrana Sinn Féin councillor killed in his home by members of the Ulster Defence Association in 1991, have criticised the Gardaí's handling of the investigation and in 2005 they started a campaign for an inquiry.
The Smithwick Tribunal is also investigating allegations of collusion following the deaths of two Royal Ulster Constabulary officers killed by the Provisional IRA as they returned from a meeting with the Gardaí in the Republic of Ireland following a recommendation from the Cory Collusion Inquiry.