As Māori society began to disintegrate, the justice system mopped up those who were deemed a public nuisance. In the 1930’s Māori “lads” were sent off to borstal “in their own interests” because they were judged to have come from bad surroundings – a practice since taken over by youth justice institutions. In 1902, Māori constituted 2.8 percent of all prisoners received – by 1934 that number had risen to 8.9 percent. Prison sucked up all types of offenders from the lower strata of society: the small time repeat offenders, drunks, vagrants, the mentally ill, and so on.
By the 1930’s, while New Zealand had very little crime, it had an average prison population three times greater in proportion to the general population, than that of England and Wales.
Prison provided social benefits: it hid our failures from view; it allowed politicians and the courts to maintain public credibility; it satisfied a public demand for retribution.  New Zealand had become a punitive and mean-spirited society. 
The impact of the Māori urban migration of the 1950’s was predictable.  Between 1954 and 1958, reported Māori youth offending rose by 50%. One of the factors that caused this increase related not to how Māori behaved in this strange and new urban world but how they were treated by non-Māori. Māori urban migrants were perceived and treated as a potentially dangerous underclass. We were outsiders.
The Police, like much of the public service in the 1950’s was unapologetically monocultural. In 1951, the Police boasted one Māori police officer, Bill Carran, who had joined the police in 1920, and retired in 1958, as an Assistant Commissioner. Carran, of mixed descent, was referred to disparagingly as ‘the Black Tracker’ by his colleagues, and survived by downplaying his Māori heritage, and emphasising his pākehā side. 
When Commissioner JB Young canvassed his staff in 1950 about recruiting Māori , he found them ‘almost unanimously opposed’. The Senior Sergeant at Taihape commented:
The average European would strongly resent being corrected or reprimanded by a Maori, particularly in some districts where the colour line is still observed. On the other hand, the average Māori appointee would be inclined to suffer from an inferiority complex when dealing with Europeans, or be imbued with authority and fail to use discretion when dealing with Maoris.”  Continue reading The Impact of Race Relations on Criminal Justice