John Cullen was born in Glenfarne, County Leitrim, Ireland, and baptised there on 28 March 1850. He was the son of Mary McNulty and her husband, Patrick Cullen, a farmer. Details of Cullen's life are unknown until he joined the Royal Irish Constabulary in 1869. He married Rachel McGinley on 6 May 1874, at Killygordon, County Donegal; they had at least five sons and three daughters. He resigned his position in March 1876 in order to go to New Zealand. On the passage out on the Camperdown he was appointed a constable to police the passengers.
On 20 July 1876 Cullen joined the New Zealand Armed Constabulary. He was the first person to graduate from the Armed Constabulary depot into the police branch of the unified New Zealand Constabulary Force then being established. In January 1877 he was posted to Blenheim, where he won high praise from his superiors and was promoted to sergeant on 1 July 1878. He quickly established a reputation as a disciplinarian, and survived a number of accusations of overbearing behaviour towards his men and the public. Cullen moved steadily through the three NCO classes, serving in Dunedin, Timaru, Christchurch, Napier (where he was in charge of a sub-district from 1891) and Wanganui. In 1897 he was sent on a special undercover assignment to the prohibitionist King Country, to entrap sly-grog sellers. He travelled disguised as Mr Berkeley, life insurance agent, securing the convictions of 26 prominent violators of the licensing laws and much praise from authorities harried by temperance campaigners.
On 20 September 1897 Cullen was promoted to the position of inspector, third class, even though he ranked only 12th on the list of first-class sergeants in what had become the New Zealand Police Force in 1886. As the most junior commissioned officer he was posted to Greymouth, in charge of the Nelson and Westland District, but in 1898 was sent to relieve at the most important district covering Auckland, Waikato, the Bay of Islands and other northern areas; he was confirmed in permanent charge in December.
Cullen's disciplinarian style differed markedly from that of the modernising Commissioner J. B. Tunbridge: 'I am naturally a strict man', he acknowledged. But Cullen appreciated Tunbridge's professionalism, and Tunbridge and his successor, Walter Dinnie, needed a tough inspector to clean up 'a state of great disorganization' in Auckland. They were prepared to overlook serious indiscretions, which included open feuds with subordinates and important local public figures, and Cullen's vindictiveness towards the many he had fallen out with. Cullen, who was of imposing presence with penetrating eyes, 'stern-looking and officious', kept tight control over his men through a system of espionage run by his favourites within the Auckland district police and by civilian observers. Many felt that the methods of 'Czar Cullen' went beyond strictness and into the realm of the unscrupulous.
It was no secret that Cullen had aspired to the commissionership on Tunbridge's retirement; he was disappointed again when Dinnie was forced to resign at the end of 1909 following a commission of inquiry. He blamed his failure to gain the position on anti-Catholic influence. Criticism of some of his methods by Stipendiary Magistrate Charles Kettle, and accusations by Dinnie that he allowed personal animus to overcome his better judgement, cannot have helped.
With the Police Force now placed under the interim regime of Frank Waldegrave, the under-secretary of justice, Cullen's expertise was needed all the more. His most vocal support came from those who appreciated his active encouragement among young policemen of sports such as athletics, boxing, wrestling and ju-jitsu; and from the Reform Party, whose leader, William Massey, declared in 1911 that Cullen would make an excellent commissioner. Even former opponents such as New Zealand Truth argued strongly for him to be given the chance to take a firm grip on the force. With Waldegrave's retirement, the short-lived Liberal government of Thomas Mackenzie appointed Cullen as commissioner of the New Zealand Police Force on 17 April 1912, despite 'determined, if not actual diabolical' opposition to him. He was the first commissioner to rise from within the ranks of the force.
In July 1912 the conservative Reform government came to power, headed by Cullen's supporter, Massey, and with his close friend Alexander Herdman as minister in charge of police. They gave Cullen great scope for his propensity to wield force against the 'enemies of order'. The new government's response to a strike at Waihi by miners affiliated to the militant New Zealand Federation of Labour provided the opportunity. Under police protection the mines were reopened with the use of strike-breaking labour; strikers were gaoled en masse for activities previously tolerated; and strike-breakers were encouraged to take over the town from the strikers. Observers commented that whenever Cullen appeared in Waihi – where eventually over 80 police (10 per cent of the force) were stationed – the level of confrontation escalated, sometimes developing into pitched battles. The morning after Cullen persuaded the miners to withdraw pickets from their hall, the strike-breakers – marching past, flanked by police – attacked it, and in the mêlée, striker F. G. Evans was fatally injured. In an ensuing reign of terror by the strike-breakers, many of the 'Red Feds' and their families were forced to leave Waihi.
In 1913 the government dealt militant unions – now grouped in the United Federation of Labour – a decisive blow by crushing the great strike focused on the waterfront. Regular police power was complemented by contingents of special constables: mounted men ('Massey's Cossacks') from the countryside and 'foot specials' from the cities. Class and sectional hatreds were virulently displayed in violence between strikers and the forces presided over by an enthusiastic Cullen. During a clash at the corner of Wellington's Buckle and Taranaki streets on 3 November, several bullets whistled perilously close to him. After the crushing of the strike and the UFL, he devoted considerable effort to covering up over-zealous and extra-legal behaviour by the special constables.
By now Cullen had already firmly stamped his mark on the Police Force. Long-awaited new police regulations had replaced the outdated 1886 rules, and a new Police Force Act had been passed. These measures codified the situation which had emerged as a result of reforms introduced by Tunbridge and his successors, and effected improvements in the conditions of policemen. But they also reaffirmed aspects of the tight discipline of the past. Soon after release of the new regulations, Cullen and Herdman crushed an attempt by policemen to establish a police union; and during the 1913 strike, Superintendent A. J. Mitchell was humiliated and effectively demoted by being withdrawn from command of policing in Auckland for allegedly being too soft on strikers.
With the advent of the First World War the police were obliged to take on many extra duties: supervising enemy aliens, enforcing emergency regulations, keeping a watch on dissidents, hunting for spies, suppressing pacifist and socialist opposition to the war. Cullen and Herdman kept an iron grip on the police war effort, and ensured that the quality of policing did not suffer as increased duties fell upon the shoulders of fewer experienced men. While criticisms of Cullen's handling of internal matters continued – for example, his alleged favouritism in promotions and perquisites – even critics conceded that the lot of the ordinary policeman had improved immensely.
The last year of Cullen's commissionership gave him a final chance for adventure and glory. In early 1916 the government decided to suppress the activities of the prophet Rua Kenana, who was challenging the authority of the state and encouraging Maori to refuse to participate in the war effort. Cullen headed an expedition of several dozen policemen to Maungapohatu, Rua's capital deep in rugged bush territory in the Urewera. Owing to his clumsy handling of the attempt to arrest Rua for failing to answer a summons on liquor charges (an effort later deemed to have been illegal), a gun-battle ensued in which two of Rua's closest followers (including his son) were killed. Cullen later, unavailingly, hounded some of the resistant Maori and their lawyers with 'his usual vindictiveness' and (it was widely believed) with some use of police perjury.
Cullen had been due to retire in May 1916, but he needed little prompting from Herdman to take the maximum possible extension to 23 November. On his retirement he was appointed to the Imperial Service Order, and in August 1917 became the first New Zealander to be awarded the King's Police Medal. Cullen was then given the position of commissioner of aliens in the Defence Department. He found compulsory employment for and supervised enemy aliens, mostly unnaturalised Dalmatian gum-diggers. When there was resistance to compulsory manpowering (at piece-rates), particularly after the end of the war, he branded this as 'shirking' or 'Bolshevism', threatened to expel the ringleaders from New Zealand, and secured the internment or gaoling of offenders.
The position of commissioner of aliens was disestablished in early 1919 and Cullen retired to private life. Rachel Cullen had died on 20 June 1917, and on 11 June 1928 he married Ellen Margaret Hendrey at Auckland. He divided his time between his home in Remuera and work on acclimatisation matters in Tongariro National Park, where he had a bach. He was an honorary warden, and served on the park's board from 1923. He and Herdman introduced heather to their beloved Tongariro, and together shot pheasants in the manner of country gentry. Cullen died at Auckland on 26 October 1939, survived by his second wife and four children of his first marriage.
After John Cullen's appointment as commissioner of police, a new, conservative government had required a harsh crackdown on the perceived enemies of order. Cullen's willingness to oblige, sometimes with scant regard to legal niceties, made him one of the most controversial police leaders in New Zealand's history.