A teenager set to be tried for a second time for the murder of a retired Bay of Plenty teacher in 2008 has pleaded guilty to the charge.

Lori-Lea Waiora Te Wini, now 17, admitted a charge in the High Court in Rotorua on Thursday of murdering 79-year-old John Rowe, who was found dead in Opotiki, 130km east of Rotorua, on November 25, 2008.

Te Wini, who was 14 at the time of the attack, was originally convicted of murder after a trial in 2009 but the Court of Appeal granted her a retrial after an appeal.

Thursday's plea was made four days before her retrial was set to begin.

Te Wini's cousin Courtney Churchward, who was 16 at the time of the offence, was originally jailed for life, with a minimum non-parole period of 17 years, after being found guilty of murder.

Her minimum term was later reduced to 13 years by the Court of Appeal but the court refused to overturn her conviction.