The case has prompted intense intrigue as the bodies of the man and his 11-year-old stepson were never found in the rough waters of Blue Cod Bay.
Mike’s mother, Fiona Lu, believes the duo faked their deaths and fled the country and wanted the investigation to remain open.
Ms Lu said Mr Beckenridge — a licensed helicopter pilot and experienced yachtsman — was calculating, capable and resourceful and believed he had the skills to successfully escape undetected with her son.
Reported sightings of the pair after their disappearance on March 20, 2015, supported her theory, she said.
But more than 10 years after Mr Beckenidge’s Volkswagen launched off the cliff, in a decision released this week following a hearing in 2023, Coroner Marcus Elliott ruled that theory was implausible.
"Mr Beckenridge’s actions illustrate that he either did not have, or did not display, the characteristics of the intelligent, resourceful, rational and well-prepared criminal Ms Lu ... believe[s] him to be," the coroner said.
"His actions were in fact those of a man who was desperate and irrational, making things up as he went along and driven by a desire to lash out at those he perceived to have done him wrong."
The disappearance came after Family Court proceedings between Ms Lu and Mr Beckenridge, which saw Mike placed in his mother’s care.
While at her Invercargill home, the boy was secretly communicating with his stepfather, professing his love and lamenting the situation.
The covert conversations continued until March 13 when Mr Beckenridge abducted Mike from his school.
For the following week, the duo were effectively on the run.
They set up camp on a cliff top, south of Curio Bay and tea bags and a toothbrush found there indicated they likely stayed overnight on March 19, the coroner found.
On March 20, around 1.15pm, a police car drove along nearby Mair Rd.
The coroner said Mr Beckenridge would have feared arrest, and "the situation went from desperate to dire".
He drove off the cliff with Mike shortly after, the coroner ruled.
The coroner said it was indicative of a trial run by Mr Beckenridge followed by the final plunge.
Supposed sightings of the pair since had fuelled speculation, but the coroner said the facts pointed to them being dead.
"The evidence relating to Mr Beckenridge leading up to his disappearance reveals him to have been angry, self-righteous and vengeful, even at times delusional," the coroner said.
"This is consistent with him carrying out the act of ending his and Mike’s lives by driving the vehicle off the cliff."
