On 7 March 1842 Maketū Wharetōtara (also known as Wiremu Kīngi Maketū), the 17-year-old son of the Ngāpuhi chief Ruhe of Waimate, became the first person to be judicially executed in New Zealand. The previous November, at Motuarohia in the Bay of Islands, he had split Thomas Bull’s head open with an axe while he slept. Maketū then killed Elizabeth Roberton, her two children and Isabella Brind, granddaughter of the Ngāpuhi leader Rewa, who lived with the Robertons.

http://www.nzhistory.net.nz/culture/the-death-penalty/the-first-execution