A wealth of research has investigated associations between family structure and adverse outcomes, but surprisingly little has investigated prisoners’ childhood family backgrounds.

At September 2017, New Zealand prisons held a total of 10,470 individuals. This is an historic high. The imprisonment rate has grown steeply in the last 40 years.

If people were locked up today for those crimes worthy of imprisonment in the first half of last century (drunkenness and vagrancy for instance) our current rate would be significantly higher. In most respects (a notable exception being family violence) it has become much harder to get into prison but the numbers who do continue to escalate.

Māori make up around half of the current prison population but only 15 percent of the general population. This overrepresentation is however a relatively recent development influenced by rapid urbanisation and the loss of whanau support systems. Urbanisation also gave rise to gangs, which account for 30 percent of the prison population and whose members have higher recidivism rates.

A sharp increase in unmarried births during the 1960s correlates markedly with a later rise in the imprisonment rate. Ex-nuptial births made up 79 percent of total Māori births in 2017. For non-Maori, the corresponding figure was 34 percent.

Prison over-representation of indigenous and non-indigenous minorities occurs in the United States, Canada, the United Kingdom and Australia. African-American, Canadian native, Afro-Caribbean and Australian Aboriginal populations all feature high rates of one-parent families.

New Zealand does not routinely collect data about the childhood backgrounds of prison inmates. But data from other developed nations shows a majority of prisoners are raised by one parent, one-parent and step-parent(s), grand-parent(s) or in state care. A minority grew up with both natural parents.

A number of studies have found that growing up with a step-parent (or serial step-parents) is a particular risk factor for later incarceration. Biological parents appear to provide a protective role which replacement parents do not.

The strongest predictor for imprisonment is growing up in state care.

Several researchers have shown that family factors – in particular, family structure – have greater impact on future risk of criminal offending than socioeconomic factors, albeit the two are closely intertwined.

New Zealand birth cohort data shows a strong flow from being known to Child, Youth and Family (CYF) as a child to becoming a Department of Corrections ‘client’ later in life. Analysis of two 1980s birth cohorts found 69 percent of incarcerated adults and 83 percent of teenage prisoners had a CYF record.

One of the strongest correlates for substantiated findings of child abuse or neglect by CYF, second only to having spent more than 80% of time on a welfare benefit, is being born to a single mother. Prison studies repeatedly find high incidence of childhood maltreatment amongst inmates, especially female.

A pronounced risk factor for becoming a prisoner is having a family member who is or has been incarcerated; especially a father. Inter-generational imprisonment has been identified in New Zealand, more strongly among Maori. Coincidental to this is the documented increased likelihood that very young Māori men will also be fathers, anecdotally, to multiple children. Further, female multi partner fertility is also associated with father imprisonment.

Evidence of bias against Māori in the justice system is not disputed. Māori over-representation in prison is also a facet of ethnic self-identification and/or identification by prison administration.