Matthews replaced Mark Byers as chief executive of the New Zealand Department of Corrections in February 2005.

In 2009 Matthews's leadership was questioned by the new Corrections Minister, Judith Collins, after a run of bad publicity that included the murder of 17-year-old Liam Ashley in a prison van;[3] the murder of Karl Kuchenbecker by Graeme Burton six months after he was released on parole;[4] and the Auditor General's critical report on the Probation Service's management of parolees.

[6] After an Auditor General's report was released in 2009, Collins refused to express confidence in Matthews and media commentators expected him to resign.

An enquiry into the Corrections Department was conducted by the State Services Commissioner Iain Rennie, which revealed that Corrections had made efforts to improve and had warned the government of the day and the previous government that under-resourcing was putting public safety at risk.

After his resignation, Matthews listed the installation of cell phone blocking technology at prisons throughout the country, better sentence compliance by the Probation Service and the establishment of the Professional Standards Unit which investigates corruption by prison officers as his top achievements while he was Chief Executive.