Mr Nassir Bare claimed the police officers smashed his teeth against a gutter, capsicum-sprayed him when he was handcuffed, kicked him in the ribs and racially abused him.

Mr Bare complained to the now defunct Office of Police Integrity in 2010 about the alleged attack, claiming he had been the victim of "cruel, inhuman and degrading treatment", but the OPI director decided not to investigate.

Mr Bare took the case to the Supreme Court, claiming the decision by the OPI, which has since been replaced by the Independent Broad-based Anti-corruption Commission, had violated his human rights. He lost the case but then decided to appeal.

In a majority 2-1 decision, the Court of Appeal's Justices Pamela Tate and Joseph Santamaria on Wednesday upheld the appeal. Chief Justice Marilyn Warren said she would have dismissed the appeal.

The appeal judges found the OPI's decision was unlawful and ordered the matter be sent to IBAC to make a fresh decision on whether it should conduct an independent investigation into Mr Bare's complaint in accordance with the Charter of Human Rights.

Mr Bare had been 17 when police stopped the car in which he was travelling on February 16, 2009.

"When he got out of the car, he alleged that a police officer pushed him up against the vehicle, handcuffed him and then kicked his legs out from under him so that he fell to the ground," the appeal judges said.

"The appellant [Mr Bare] further claimed that, as he lay on the ground, the officer pushed his head to the ground so that his chin struck the gutter.

"The officer then grabbed him by the hair and repeatedly pushed his head into the gutter and four or five of his teeth were chipped.

"His jaw was cut, which resulted in scarring.

"The officer sprayed him in the face with 'OC' [capsicum] spray several times, forcibly raising his head to do so. This caused him difficulty breathing.

"During the alleged assault the appellant claimed that the officer said words to the effect: 'You black people think you can come to this country and steal cars. We give you a second chance and you come and steal cars.'

"A second police officer allegedly kicked him in the ribs whilst he was on the ground and handcuffed."

The appeal judges said that after the alleged attack, Mr Bare complained he was taken to a nearby house where the officers held his head under water for a long period and told him to wash his eyes or he would go blind.

"He was then told he was under arrest and taken to Williamstown police station in the back of a police van. While in the cells at Williamstown police station, ambulance officers said he needed stitches but an officer said, 'No he can go in his own time'.

"The appellant suffered pain, injury to his teeth and jaw, bruising and humiliation as a result of the alleged serious assault."

Mr Bare was not in court for the judgment.

Youthlaw's advocacy and human rights officer, Tiffany Overall, said there was a need for independent investigations into complaints made against police.

Complaints against police are usually handled by the department's Police Standards Command.

"Currently few young people have the confidence in the system to make complaints," Ms Overall said in a statement.

"However, we believe a fully independent investigation process would see the number of complaints from young people and adults substantially rise.

"An independent and robust investigation of complaints against police would ensure that police who engage in abuse are prevented from perpetrating further harm, would deter future human rights abuses, and instil greater confidence in Victoria Police."

Ms Overall called on the Andrews government to strengthen the legislative powers and resources of IBAC so that all investigations into police human rights abuses were conducted independently of Victoria Police.