Research interests include crime and criminal justice and social history.
- Newbold G. (2016) Crime, Law and Justice in New Zealand. New York: Routledge. 1-285.
- Newbold G. and Hough D. (2009) Salisbury Street Foundation: 1979-2009 30th Anniversary. Christchurch: Salisbury Street Foundation. 27pp.
- Newbold G. (2007) The problem of prisons: Corrections reform in New Zealand since 1840. Wellington: Dunmore Publishing Ltd. 339pp.
- Dennehy G. and Newbold G. (2001) The Girls in the Gang. Auckland, New Zealand: Reed. 208.
- Newbold G. (2000) Crime in New Zealand. Palmerston North: Dunmore. 279.