The family of a south-western Sydney man have alleged police "brutally bashed" their son outside their home and wrongfully accused him of assaulting police, resisting arrest and being in a police pursuit.

Police allege 23-year-old plumber Omar El Baba was the driver of a car involved in a police chase on May 28 at 10:44pm, an accusation El Baba denies.

According to police, a few hours later that night officers from Green Valley Police Station found the same car they believed to be involved in the pursuit outside a home in Heckenberg with El Baba and a woman sitting inside.

They said El Baba failed to produce his licence, became violent and assaulted police.

He was then arrested and taken to Green Valley Police Station before being released to Liverpool Hospital for treatment for what police said were "minor injuries".

El Baba's lawyer also claimed his client was only charged when a complaint was made later that day after he was discharged from hospital.

El Baba was charged with assaulting police, resisting arrest and custody of a knife in a public place.

But he gives a different version of events and denies he was involved in the police pursuit, saying he was out with friends that night.

"My friend came over, picked me up, went to Bankstown to go grab a feed," El Baba said.

He said later that night he was in his car outside of his house on St Johns Road when one police officer told him to get his licence otherwise he would be detained.

"I got scared and told him 'I live here, I'm going to go get my licence'."

'I thought they were hitting to kill me, they wouldn't stop'

El Baba alleged when he came outside with his licence, there were over 20 police officers including officers from the riot squad.

"I told them they're not allowed [inside the house] because I felt scared," he told the ABC.

"Then they all just rushed in and attacked me."

He claims the police did not say he was under arrest or tell him they intended to take him to the police station.

"They slammed me on the floor then they started kicking me, punching me, kicking my groin area," El Baba said.

He told the ABC the police said repeatedly: "You 'effing' Lebo, that's what you deserve".

"I thought they were hitting to kill me because they would not stop."

"I was on the floor in front of my family getting stomped on, getting stomped on, and kicked in my face like a soccer ball."

El Baba's sister Mona said she heard her brother's screams for help and ran outside to see "the most brutal excessive force I have ever witness in my entire life".

"I saw police officers everywhere, punching my brother, kicking him, kneeing him, elbowing him on his head, his neck, his back," Ms El Baba told the ABC.

"I could see my brother's face was absolutely horrific, he was bleeding, and it was just blood everywhere."

'They showed no mercy, they were ruthless', sister says

Ms Baba is also a lawyer and told the ABC she pleaded with officers to stop attacking her brother.

"I kept screaming out for them to stop using unreasonable force, I kept stating to them he was not resisting," she said.

"They were going to eventually kill him if they keep going.

"They showed no mercy, they were absolutely ruthless."

El Baba's father Salah said he thought the police were going to break his son's back.

"He [the police] want to break his back, I said 'you will kill him', he don't care," he said.

"He hit him in the back 'bang, bang, bang' in the face, in the head.

"The human being is not animal. If you're an animal, they never hit you like this."

New South Wales Police declined an interview with the ABC and said the case was before the courts.

Justice and Police Minister Troy Grant's office also told the ABC it would be "inappropriate" to comment on the matter before the courts and that the case was "primarily a police operational issue".

Doctor describes El Baba's physical inuries

A Liverpool Hospital emergency discharge sheet for El Baba, obtained by the ABC, stated on May 29 there was "pain and swelling on his face and head, nose and jaw, tenderness on his ribs and soft tissue swelling".

Omar El Baba alleges he was brutally bashed by police officers in his driveway. ( Supplied )

Dr Nasser Sidrak treated El Baba after he was discharged from hospital and said in a statement to the ABC that the "patient was very upset, stressed and depressed".

Dr Sirak confirmed in the statement El Baba's face was bruised and his forehead, eyes and nose were swollen.

He said El Baba had pain in his right shoulder and bruising to his knee, leg and chest.

El Baba said he suffered physical as well as mental injuries as a result of his arrest.

"All my head was literally like golf balls, all bruised lumps everywhere," he told the ABC.

"Still till now I get migraines, can't sleep properly, it hits me every now and then, I get flashbacks about what happened."

El Baba said he has not been back to work and said he is traumatised from the incident.

"It will never leave me. It will be there for the rest of my life," he said.

Next door neighbour and mother of two Slavica Duric said she was woken by the screams and looked through her window to see what was happening.

Slavich Duric said she witnessed eight to 10 police officers around Omar El Baba and said they were rough and one officer was kicking him. ( ABC News: Mohamed Taha )

"I saw 8 to 10 policemen around Omar and one of them start saying to other policemen, 'get him down, get him down'," she said.

"They start pushing him on the floor and one them started kicking him.

"They were so rough, they put his hands on his back and one of them was kicking him very badly on the legs."

Ms Duric said she was shocked because she has lived next door to the El Baba family for the past 6 years and has never had any issues.

"He's a hard worker and good neighbour, really friendly," she said.

"I'm really sorry for him."

Calls for Police Integrity Commission to investigate

El Baba's father Salah and his wife said they no longer trusted the police and were still shaken from the incident.

"Australia is a good country, free country, you can do what you like, but the police can't do this," he said.

"Everything changed in my life, I have high blood pressure."

El Baba's sister Mona said the family now wants the Police Integrity Commission to investigate and for the officers involved to face disciplinary action.

"There needs to be a clear message to police officers, they can't act outside the law and get away with it," she said.

"There needs to be transparency and there needs to be accountability and I think the only way this will happen is with an inquiry into police brutality and an investigation into this matter."

Lawyer says El Baba wasn't charged until complaint made

Omar El Baba's sister Mona informed her law firm Oxford Lawyers about the incident on the same day of the arrest.

The principal solicitor Zemarai Khatiz said his client, El Baba, had a clean record apart from a minor stealing offence several years ago.

"I've been informed that he wasn't driving the vehicle, he wasn't involved in the police chase and he did not do anything unlawful that night," he said.

Mr Khatiz said police only charged El Baba after the law firm sent a letter of complaint to Green Valley Police Station.

Omar El Baba's lawyer Zemarai Khatiz said this was the worst case of police brutality he had seen. ( ABC News: Mohamed Taha )

"He wasn't charged on the night, he was taken to the police station," he said.

"He was then taken to the hospital. He was released from the police station without any charge.

"It was only when we sent a complaint in the next day was he charged with these offences."

Mr Khatiz said El Baba will sue the police officers involved for damages, for malicious prosecution and for illegal arrest.

"It appears in my view that some of these police officers are completely out of control and it's unacceptable and the community shouldn't have to put up with it."

He said the injuries sustained to his client were severe, contrary to what was stated in the police fact sheet.

"The police have stated in the fact sheet that El Baba suffered from minor injuries," he said.

"Those are not minor injuries, those are very, very bad injuries."

Mr Khatiz said he believed the alleged excessive force could have been racially motivated.

"When my client was being kicked on the ground while he was handcuffed and not resisting and he was being kicked numerous times, one of the police officers said to him: 'you Lebo dog'," he said.

"Why would they bring someone's nationality into it?

"That's completely unacceptable."

El Baba said he is unsure why he was targeted by police.

"I don't know if it was for my background, my racial background," he said.

"I don't know what it is but you don't do that in Australia."