Police believe it is the longest-running cold case in New Zealand history to end in an arrest.
Hallett's trial in the High Court at Rotorua is expected to last about two weeks.
A spokesman for Mr Tahu's family, Colin Hair, has said the family would "certainly be taking a keen interest in things" but he did not know whether they would attend Hallett's trial.
"We are all taking a deep breath and sitting back on this one, we are sitting back and letting the system do its thing."
A former neighbour of Mr Tahu told the Herald the day after his body was found that he was a "faultless father".
"Whether his children were playing marbles or flying kites, he was always there with them," the neighbour said.
Hallett, from Rotorua, was selling homes for a Taupo real estate firm at the time.