It was the fourth time he had been convicted of drink-driving, and the consequences the most severe.
Tresler was placed in an induced coma for nearly a month.
When he woke up, the ramifications of his recklessness became starkly apparent.
Doctors had amputated his right arm above the elbow.
Unbeknown to Tresler, they had initially removed only his hand, which had been crushed during the collision but were then forced into two further amputations.
"It's my own fault," the defendant said outside court yesterday.
Counsel Chris Lynch said Tresler had lost all movement in his right shoulder and suffered ongoing pain.
That was clear as the man sat in the dock grimacing, often doubled over in discomfort.
The court heard the $20,000 Harley-Davidson Tresler was riding had been imported from the United States but had never gone through the entry compliance certification process.
It was therefore illegal to ride it on New Zealand roads.
Tresler said he had found a registration plate in a rubbish bin and fixed it to the back of the bike to give the impression it was licensed.
He was in Cumberland St early on August 1, approaching the intersection with Andersons Bay Rd and the Caversham bypass, when he lost control, court documents revealed.
Tresler, however, had no memory of the incident or the four days beforehand.
As well as the treatment for his injuries in hospital, doctors discovered a heart defect that meant the defendant needed a pacemaker fitted.
"They arguably saved your life in that regard," Judge Kevin Glubb said.
But Lynch said Tresler's new life looked very different from his old one.
A qualified diesel mechanic, he was no longer able to do that job and planned to become a tutor in the field instead.
Tresler had also played the guitar for 20 years, a hobby which now had to be cast aside.
The court heard the defendant, who was last convicted of drink-driving in 2014, had battled alcohol abuse for many years.
However, since the crash, he had been working with a psychologist and had maintained his abstinence.
Judge Glubb sentenced him to three months' community detention and 16 months' intensive supervision.
"I wish you every success with your rehabilitation," he said.