Although a mostly unarmed force, certain units of the Gardaí, such as detective units, the regional support units, and the Emergency Response Unit are commissioned to carry firearms. The original stock of Smith & Wesson Model 10 revolvers are being replaced by the Sig Sauer P226 and Walther P99C semi-automatic pistols. Regional Support Units have Heckler & Koch MP7 sub-machine guns in addition to issue pistols and non-lethal weapons such as tasers and pepper spray. They serve as a first response to back up regular Garda officers in critical situations due to a rise of incidents that involve firearm use. In order to be issued with a firearm, or to carry a firearm whilst on duty, a Garda must be in possession of a valid gun card.
Garda patrol cars are mainly white, with yellow and blue fluorescent livery whereas traffic unit vehicles adopt the battenburg pattern. The Garda crest is also present on vehicles. An Garda Síochána also use unmarked patrol cars in their duties and use of such vehicles is increasing becoming a matter of cost rather than the need to hide the vehicles, as the amendments to the exterior of the vehicle such as LED strobes, Tetra aerials and bumper LEDs in particular are extremely visible.
The Civic Guard was formed by the Provisional Government in February 1922 to take over the responsibility of policing the fledgling Irish Free State. It replaced the Royal Irish Constabulary (RIC) and the Irish Republican Police of 1919-1922. In August 1922 the force accompanied Michael Collins when he met the Lord Lieutenant in Dublin Castle.
The Garda Síochána (Temporary Provisions) Act 1923 enacted after the creation of the Irish Free State on 8 August 1923, provided for the creation of "a force of police to be called and known as 'The Garda Síochana'". Under section 22, The Civic Guard were deemed to have been established under and to be governed by the Act. The law therefore renamed the existing force.
During the Civil War of 1922-23, the new Free State set up the Criminal Investigation Department as an armed, plain-clothed counter-insurgency unit. It was disbanded after the end of the war in October 1923 and elements of it were absorbed into the Dublin Metropolitan Police.
In Dublin, policing remained the responsibility of the Dublin Metropolitan Police (DMP, founded 1836) until it merged with the Garda Síochána in 1925. Since then the Garda has been the only police force in the state now known as the Republic of Ireland, with the exception of the Military Police within the Irish Defence Forces, the Airport Police, and Dublin Port and Dún Laoghaire Harbour police forces.
First established in 1925, the Scott Medal for Bravery is the highest honour for bravery and valour awarded to a member of the Garda Síochána. The first medals were funded by Colonel Walter Scott, an honorary Commissioner of the New York Police Department. The first recipient of the Scott Medal was Pat Malone of St. Luke's Cork City who - as an unarmed Garda - disarmed Tomás Óg Mac Curtain (the son of Tomás Mac Curtain).
To mark the United States link, the American English spelling of "valor" is used on the medal. The Garda Commissioner chooses the recipients of the medal, which is presented by the Minister for Justice, Equality and Law Reform.
In 2000, Anne McCabe - widow of Garda Jerry McCabe, who was killed by armed Provisional IRA bank robbers, accepted the Scott Medal for Bravery that had been awarded posthumously to her husband.
The Irish Republican Police had at least one member killed by the RIC 21 July 1920.
The first Commissioner, Michael Staines, who was a Pro-Treaty member of , held office for only eight months. It was his successors, Eoin O'Duffy and Éamon Broy, who played a central role in the development of the force. O’Duffy was Commissioner in the early years of the force when to many people’s surprise the ability of the force to succeed despite being unarmed was established. O'Duffy later became a short-lived political leader of the quasi-fascist Blueshirts before heading to Spain to fight alongside Francisco Franco's Nationalists in the Spanish Civil War. Broy had greatly helped the Irish Republican Army (IRA) during the Anglo-Irish War, while serving with the Dublin Metropolitan Police (DMP). Broy's fame grew in the 1990s when he featured in the movie "Michael Collins", in which it was misleadingly suggested that he had been murdered by the British during the War of Independence, when in reality he lived for decades and headed the Garda Síochána from 1933 to 1938. Broy was followed by Commissioners Michael Kinnane (1938–52) and Daniel Costigan (1952–65). The first Commissioner to rise from the rank of ordinary Garda was William P. Quinn, who was appointed in February 1965.
One later Commissioner, Edmund Garvey, was sacked by the Fianna Fáil government of Jack Lynch in 1978 after it had lost confidence in him. Garvey won 'unfair dismissal' legal proceedings against the government, which was upheld in the Irish Supreme Court This outcome required the passing of the Garda Síochána Act 1979 to retrospectively validate the actions of Garvey's successor since he had become Commissioner. Garvey's successor, Patrick McLaughlin, was forced to resign along with his deputy in 1983 over his minor involvement in a political scandal. The current Commissioner, since December 2010, is Martin Callinan.
During the Emergency (as World War II was known in Ireland) there were two reserve forces to the Garda, An Taca Síochána and the Local Security Force.
An Taca Síochána had the power of arrest and wore uniform, and were allowed to leave the reserve or sign-up as full members of the Garda at the end of the war before the reserve was disbanded. The reserve was established by the Emergency Powers (Temporary Special Police Force) Order, 1939.
The Local Security Force (LSF) did not have the power of arrest, and part of the reserve was soon absorbed into the Irish Army Reserve under the command of the Irish Army.
Since 1989, the Garda has been part of United Nations peace-keeping forces. Its first mission was when a 50 strong force was sent to Namibia. Since then the force has acted in Angola, Cambodia, Cyprus, Mozambique, South Africa and the former Yugoslavia. The force's first fatality abroad was Garda Sergeant Paul M. Reid, who was fatally injured while on duty with the United Nations UNPROFOR at "Sniper's Alley" in Sarajevo on 18 May 1995.
Members of the Garda also serve in the Embassies of Ireland in London, The Hague, Madrid and Paris. Members are also seconded to Europol in The Hague, Holland and Interpol in Lyon, France. There are also many members working directly for UN and European agencies such as the War Crimes Tribunal.
Garda officers also co-operate with members of the Police Service of Northern Ireland to combat cross-border crime. They have also accompanied politicians from the Republic, such as the President on visits to Northern Ireland.
Under an agreement with the British Government and the United Nations Convention on the Law of the Sea, the Garda and the Radiological Protection Institute of Ireland are allowed to inspect the Sellafield nuclear facility in Cumbria, England.
Like every police force in the world the Gardaí have had many complaints against them including allegations of discourtesy, harassment and perjury (lying to a court). A total of 1,173 complaints were made by the public against the Gardaí in 2005, while over 2000 complaints were made in 2009.