'Callous disregard': Man jailed for one-punch attack released to return to uni

A young Perth man jailed for a sickening one-punch attack is being released so he can return to the US to study at an Ivy League University.

Joshua Billington's lawyer said it wasn't fair to call what he did a coward's punch, but a magistrate said that's what it was - and that young drunk men need to be taught not to resort to violence.

In a car park, victim Mitch Davis didn't see what was coming his way.

One punch knocked him unconscious in a moment of what the magistrate called "unjustified violence."

But it's what Joshua Billington did next that the magistrate said showed a "callous disregard and lack of remorse" - he walked away with a casual glance, offering his victim no help.

Mitch Davis was left with bleeding on the brain and needed eight staples in his head.

Joshua Billington has never apologised for the attack and had nothing to say when questioned outside court on Wednesday.

The US college track star was sentenced to nine months in prison for the attack, started when one of his friends began harassing the victim's girlfriend.

Billington said he thought his mate was going to get hit, but magistrate Elizabeth Woods said there was no threat and that it was an unprovoked attack carried out "with speed and force."

Late on Wednesday afternoon, bail was granted so that Joshua Billington can fly back to the US for exams at prestigious Princeton University.

Late this afternoon, bail was granted so Joshua Billington can fly back to the US for exams at Princeton University.

Lawyer Tom Percy said Billington believed the sentence was "excessive" and had instructed his lawyers to make an immediate appeal.

Asked what his message for other young men in Perth's entertainment districts were, victim Mitch Davis's advice was simple: "Watch your back."