Nicole Tuxford was raped and murdered by Paul Tainui in April 2018, while he was on parole following a similar murder more than 20 years earlier.
In 1994, Tainui, then known as Paul Russell Wilson, raped his ex-girlfriend Kimberley Schroder before stabbing her to death.
He served 13 years for her murder before being granted parole in 2010.
During his prison sentence, he met David Bain and the two became close friends, with Tainui a groomsman at Bain's 2014 wedding.
At the time of Tainui's second murder, long-time Bain advocate Joe Karam told RNZ Bain was "shocked to the core" to hear Tainui had killed again.
Karam said he thought the Parole Board made a mistake when they allowed him out.
Tainui was given one of the country's toughest sentences for Tuxford's murder in 2019 - life imprisonment with a minimum 28 years without parole.
Coroner Marcus Elliot will look at Tuxford's murder alongside the suspected suicide of Gary Schroder, the father of Tainui's first victim.
The inquest is expected to run for two weeks.
