Timeline: How Garda has rolled from crisis to crisis
2012: Allegations emerge about gardaí cancelling penalty points for motorists.
2014: Then Garda Commissioner Martin Callinan appears before TDs and describes the actions of whistleblowers Sergeant Maurice McCabe and John Wilson as "disgusting". Barrister Seán Guerin is asked to look into the penalty points allegations. In March, Mr Callinan announces his retirement after a late-night visit to his home by the then secretary general of the Department of Justice. It came ahead of revelations about the practice of recording non-emergency phone calls in Garda stations. In May, Alan Shatter resigns as Justice Minister. Frances Fitzgerald takes over.
2016: The O'Higgins Commission report investigating other allegations by Sgt McCabe is published in May. It finds that Mr Shatter took Sgt McCabe's allegations seriously and that the whistleblower acted out of legitimate concern.
Commissioner Nóirín O'Sullivan denies that she regarded Sgt McCabe's actions as "malicious" after reports claimed that her legal team was instructed to attack his motivation and character.