Sydney backpacker stabber jailed

A man who can't explain why he "went crazy" and stabbed three backpackers with a piece of glass in Sydney has been sentenced to at least nine years in jail.

Timothy Kelly, 37, viciously attacked two 19-year-old German men and a 24-year-old Irish woman outside a hostel in the city's CBD early on the morning of October 3 last year.

He was handed a maximum sentence of 12 years on Friday after pleading guilty to six charges, including two counts of wounding a person with intent to cause grievous bodily harm.

Downing Centre District Court heard Kelly had been staying at the Cosy Private Hotel on Pitt Street in the months following his May release from 8-months in prison.

One night he woke about 2am, smashed a window in his room and filled a sock with the broken glass.

He then went outside to where the trio of backpackers were sitting on the front steps of next door's Westend Backpackers hostel.

The then 36-year-old approached and stabbed German, Christoph Leibrecht, in his left forearm and tried to pierce his right thigh through his jeans.

Kelly then grabbed his companion Lukas Kofink from behind and jabbed him in the neck five times, just missing his carotid artery and causing substantial blood loss.

Irish woman Aifric Butler-Rees was slashed through her upper lip, cutting it in half.

The frenzied assault only stopped after a quick-thinking Thai backpacker stepped in.

The 29-year-old leapt to the group's defence receiving a cut to his arm and torso in the process but prompting the glass-wielding Kelly to chase four or five other people down Pitt Street.

He was eventually detained by a security guard at a nearby pub until police arrived.

Kelly, who represented himself, told the court he did not contest any of the charges but could not explain his behaviour.

"It is just crazy you know, absolutely crazy," he told Judge Reginald Blanch.

Kelly said he had been addicted to heroin and morphine for about a decade but declined Judge Blanch's offer for legal representation so he could get psychiatric and psychological assessments.

"He was released as a lost soul into the community without any support," Judge Blanch said.

Kelly will be eligible for parole in October 2022.