An officer who's spent over 30 years as part of New Zealand's police force has detailed his experience in a new book.

David 'Chook' Henwood was a key part in the development of criminal profiling in New Zealand – a game changer for policing in the nation.

He retired in 2007 and has now shared his story, and his thoughts on policing, in his new book Unmasking Monsters. 

He says he witnessed the factors that led to generational crime - which go deeper than upbringing. 

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