A US student who was jailed for six months for sexually assaulting an unconscious woman has been freed after serving half his term.

Brock Turner, 21, was convicted in March of attacking the young woman after they drank heavily at a fraternity party at Stanford University, California.

The victim told the court that she had woken up hours after the attack with dried blood on her hands and no memory of meeting Turner or being taken to hospital.

Turner, who dropped out of Stanford after his arrest, said the woman had been awake and conscious throughout the incident.

The case sparked an outcry across the US after critics claimed the sentence was lenient and the victim spoke of the "irreversible damage" she suffered in a statement that was widely circulated on social media.


Image: The 21-year-old must register as a sex offender for life

Prosecutors pushed for a six year prison sentence, but Santa Clara County judge Aaron Persky cited the "extraordinary circumstances" of Turner's youth and handed the student a six-month sentence.

After a backlash Mr Persky voluntarily removed himself from hearing criminal cases.

District attorney Jeff Rosen said that the judge's sentence "does not fit the crime".

Following his release, Turner faces three years of unsupervised probation and must register as a sex offender for life.

Image: Turner was formerly an Olympic hopeful swimmer

The 21-year-old is also is barred from parks, schools and other places where children are expected to gather.

His neighbours will be sent postcards informing them that a sex offender is moving in nearby, Greene County sheriff Gene Fischer said.

Another sheriff, Laurie Smith, said that Turner was given a large packet of hate mail on his release.

She added: "There was a lot of hate."