Christchurch builder Michael Craig McGrath, 49, was last seen at his Halswell home nearly six years ago.
The 54-year-old murder accused David Charles Benbow, who was arrested in September 2019 on a charge of murder with a firearm, has pleaded not guilty to the killing.
McGrath was last seen at his Halswell home in May 2017 and his body has still not been found.
The disappearance sparked an extensive missing persons inquiry, tagged Operation Renovation, with more than 100 people involved during some phases of the search.
The trial begins in the high court under Justice Eaton after multiple adjournments to proceedings.
The death of the defence's lead counsel Margaret Sewell in November 2021 affected trial preparations.
A new date of 13 February 2023 was earmarked, but the trial was brought forward six months amid concerns around the amount of time the accused was to spend behind bars awaiting trial.
Covid-related sickness last year caused further setbacks, ahead of a scheduled trial date last August.
Benbow was bailed to a property in Dargaville in November 2021, and was not allowed to enter the South Island without court approval.
He was held in custody for more than two years following his arrest before his successful bail application.
