John O'Donovan was born at Ross Carbery, County Cork, Ireland, on 22 May 1858, the son of Mary Hegarty and her husband, Florence O'Donovan, a farmer. John grew up in a large Catholic family and later became a teacher under the national school system in County Cork. In 1878 he arrived in New Zealand to join his brother Richard, a contractor who had represented Okarito in the short-lived Westland Provincial Council. Although farming was probably his initial intention, John became a third-class constable in the police branch of the New Zealand Constabulary Force at Hokitika on 1 April 1879. Another brother, Florence, joined the force in the same month. Soon after appointment John was stationed at Wellington, where he remained for 15 years.
Promotion to second-class constable came in November 1881. Two years later O'Donovan applied for promotion to first-class constable but police retrenchment and restructuring had eroded his seniority. He came to believe that transfers and promotions resulted from political and personal influence. However, O'Donovan was seen as energetic, attentive and efficient, and around 1886 he became watch-house keeper at Wellington police station.
In January 1890 O'Donovan sat the first and only police examination offered before 1907, achieving the second-highest marks. With merit now reinforcing his claim of seniority, O'Donovan was made a first-class constable in March 1890 and became court orderly. More regular hours allowed time for further study of law, and for courting. On 31 August 1892, at St Mary's Cathedral, Wellington, he married Josephine Whitaker, née Hark, a widow. Looking for a rent-free house and extra income from non-police duties O'Donovan applied for a vacancy at Stratford in 1894. Doubting his chances, he sought the aid of political friends. Such influence he deplored in principle, and it proved unnecessary as his superiors saw him as well fitted in every respect for the position. About this time, O'Donovan qualified as a solicitor.
Although his predecessor at Stratford had suffered a breakdown, seemingly through overwork, O'Donovan coped with wide-ranging duties in addition to local court work that doubled in two years. Again he impressed his superiors, and after being promoted to third-class sergeant in January 1898 he was transferred to take charge of the Hawera station.
O'Donovan soon sought a transfer back to Wellington to assist the family of his brother Florence, who had drowned near Napier in April 1897 while attempting a rescue. Shortly after returning O'Donovan gave evidence in May 1898 to the Royal Commission on the Police Force of New Zealand concerning the inadequate compassionate allowance for families of police who lost their lives on duty, and sources of discontent amongst the rank and file. He emphasised the need for police examinations and a better system of training.
In December 1898 O'Donovan became the first instructor at the training depot opened at Mount Cook station in Wellington. While there he set a pattern of recruit training that endured until the early 1950s. In June 1901 he was put in charge of police accompanying the tour by the duke and duchess of Cornwall and York. Promoted to sub-inspector in July 1902, O'Donovan supervised Wellington city police and prosecuted in the Magistrate's Court, gaining kudos from the Bench and the Bar. He was transferred to Palmerston North in 1908 and promoted to inspector in charge of Invercargill district in 1911. The following year he took command of Napier district and in 1915 was promoted to superintendent at Dunedin. In November that year he took charge of the Wellington district, standing in for Commissioner John Cullen when required. He became commissioner on 1 December 1916.
For Commissioner O'Donovan the next five years were a period of exceptional stress and difficulty in meeting the demands of war and the transition to peace with insufficient police and inadequate facilities. He believed his firm application of the war regulations prevented a state of turmoil and upheaval. In 1920 he began a system of covert political surveillance that lasted until August 1957 when the New Zealand Security Service assumed responsibility. Much tighter control of firearms was implemented. For services during the visit of the prince of Wales he was made an MVO in May 1920.
From 1918 O'Donovan sought to resolve outstanding administrative issues. The New Zealand Public Service Association was permitted to represent rank-and-file police. The relative status, pay and promotion prospects of the uniformed and detective branches were finally determined and an eight-hour shift system inaugurated. Pay increases also maintained morale and police districts were expanded from 9 to 14. Although O'Donovan wished to extend the basic police training to include more specialised technical instruction for detectives and sergeants, he managed only to reopen the depot for recruits that had been closed during the war.
In his preface to a new set of police regulations in 1920, O'Donovan summed up eloquently his philosophy of impartial, firm but beneficent policing by 'peace officers', emphasising that police prestige depended on personal character and conduct. He urged civility and restraint such that the use of the baton 'be scrupulously proportioned to the need'; such dicta were quoted by police decades later. O'Donovan believed it was essential that no unauthorised influence outside the force should shape police conduct or be sought to redress grievances. More clearly than hitherto he maintained the concept of police independence from political interference.
By 1921 pressure of work had affected O'Donovan's health and he retired on 31 December, 18 months before the end of his term. He had built on developments in the force since 1898, establishing an organisation, ethos and pattern of administration that remained largely unchanged for the next 45 years. For the rank and file, O'Donovan's style of leadership was more benign than that which had previously prevailed.
In 1922 O'Donovan was appointed an ISO and visited Britain and Ireland. He died at Wellington on 8 April 1927, survived by his wife, three sons and a daughter. Attendance by public dignitaries at his funeral, conducted by Archbishop Thomas O'Shea, and the procession led by 60 police through the city, underlined John O'Donovan's high standing in the community.
Physically smaller than many fellow officers, John O'Donovan stood out in personality. A carefully trimmed goatee gave an air of distinction to 'a man of gentle manner and fine sensibilities'. A repeated observation was that this quiet kindly man would have made a good priest. Wide reading enriched an eloquence that claimed respect: his funeral oration at the graveside of a constable killed on duty moved the government to extend the coverage of war pensions to police. A prominent and staunch Irish Catholic at a time of sectarian tension, John O'Donovan was seen as 'a remarkably able and fair-minded man – one of the most gentlemanly officers in the Public Service'.