Oswald Chettle Mazengarb was born in Prahran, Melbourne, Australia, on 31 May 1890, the son of Alfred Valentine Mazengarb and his wife, Elizabeth Mary Murphy. At the time of Ossie’s birth his father was a phrenologist, but he later became a pastor, first in the Associated Churches of Christ and later as a Baptist. His family moved to New Zealand soon after his birth and he was a pupil at Otago Boys’ High School from 1903 to 1905. On leaving school he worked for a newspaper before enrolling at the University of Otago in 1908. He graduated BA in 1911 and, with the assistance of the Macandrew Scholarship in political economy, graduated MA in 1912. That year he moved to Victoria College to study law. At university he was a keen sportsman and had represented Otago University at athletics and debating. In his first year at Victoria College he won the Plunket Medal for oratory. He completed his LLB in 1914, and graduated LLM in 1917.
Mazengarb was admitted as a barrister and solicitor of the Supreme Court in 1914. The following year he went into partnership with J. S. Barton. On Barton’s appointment as a magistrate in 1918, Mazengarb was joined by E. P. Hay and R. L. Macalister. The firm of Mazengarb, Hay and Macalister rapidly became one of the largest law practices in Wellington.
Mazengarb married Margaret Isabel Campbell in Invercargill on 6 April 1920. They were to have three daughters. He was a devoted father and from 1934 was a member and later chairman of the board of governors of Queen Margaret College in Wellington.
The emphasis of Mazengarb’s practice was on civil jury cases. In the heyday of personal injury litigation he became an outstanding advocate with a natural flair for dramatic presentation, almost always on behalf of injured plaintiffs. He had a talent for sensing the winning potential of some circumstance in the case that would have a profound influence on a jury. And he was a master tactician – an attribute that did not always endear him to his professional opponents. He had a keen ear for the telling phrase and did not hesitate to play on the jury’s emotions, even to the point of engaging in melodrama.
With the introduction of compulsory third-party motor vehicle insurance in 1929 there was an upsurge in litigation by people who had been injured in traffic accidents, and Mazengarb made it a speciality. As a result of this experience he wrote The law relating to negligence on the highway (1942). The book was based on a dissertation he had submitted for the degree of LLD from the University of New Zealand in 1939. Highly praised by the examiners and later by reviewers, it became the standard text.
In 1947 Mazengarb retired from the firm and was appointed King’s counsel, a recognition of his eminence as an advocate. He also appeared as counsel before the Royal Commission on Monetary, Banking and Credit Systems in 1955–56. He had earlier appeared before the Royal Commission on Gaming and Racing in 1947, but that kind of work was not to his taste: it lacked the glamour of the court room drama of a jury trial.
Mazengarb’s forays into politics were not a success. He stood as a candidate for the New Zealand National Party in Wellington East in 1935 and for Wellington Suburbs in 1938, but in neither instance was he able to stem the tide in favour of the Labour Party. On 22 June 1950 he was appointed to the Legislative Council, a brief and inglorious membership of the body that he and 24 others appointed at the same time had undertaken to abolish. He was appointed a CBE in 1953.
On 23 July 1954 he was appointed by the government to chair the Special Committee on Moral Delinquency in Children and Adolescents, which was set up after an outcry over teenagers’ behaviour in Lower Hutt. Mazengarb dominated the committee and its proceedings: mindful of the National government’s wish to have the report completed before the imminent general election he set the timetable for the committee’s investigation, dictated the tasks to be performed, and wrote or edited much of the report. Other committee members considered him ‘a puritan moralist’ and ‘fundamentalist’. The report blamed lack of parental supervision for juvenile delinquency and advocated a return to Christianity and traditional values. It provided a basis for new legislation and Mazengarb assisted with the drafting of three acts recommended by the committee in its report: the Indecent Publications Amendment Act 1954, which widened the definition of ‘obscene’ and ‘indecent’; the Child Welfare Amendment Act (No 2) 1954, which enabled the Children’s Courts to treat children engaging in sexual behaviour as delinquent; and the Police Offences Amendment Act 1954, which made it an offence to sell contraceptives to children under 16 years of age. The government sent a copy of the committee’s report into every home in the land, but social issues were not a major factor in the following election.
Mazengarb had many wide-ranging interests outside his law practice. From 1953 to 1963 he was a member of the New Zealand Road Safety Council. He was a keen member of the Wellington Shakespeare Society, where he delighted in stage appearances, and of the New Zealand Haemophilia Society. He was president of the Wellington Rose Society from 1947 to 1949, chairman of the Kelliher Art Competition Trust, and an officer of the Masonic Grand Lodge of New Zealand. An activity that lay close to his heart was the work of Heritage (Wellington), which was concerned with the welfare of children of men who had died on active service; up to the time of his death he was president of the Wellington society and of its national organisation. In 1962 he wrote its history, The story of Heritage. Towards the end of his career Mazengarb wrote Advocacy in our time , in which he expressed his views about the function and importance of advocacy in a democratic society, but chiefly gave wise guidance to counsel who wished to specialise as advocates. The book was published posthumously in 1964.
Mazengarb was short and stocky in build, a man of charm, wit, and eloquence. He died at Wellington on 27 November 1963, survived by his wife and daughters.