UPDATE: A NAKED and unarmed teenager shouted for God to help him as he was beaten by uniformed police officers in a Byron Bay laneway, a public hearing has heard.

The hearing at the Law Enforcement Conduct Commission began on Monday and is probing whether the four officers involved in the notorious incident used excessive force on the 16-year-old boy in the early hours of January 11 2018.

The confrontation in Lateen Lane, near Nomads Backpackers Hostel in the popular northern NSW town, was broadcast on national television soon afterwards, sparking community outrage and prompting the official investigation.

Explosive raw footage of the altercation, captured on a mobile phone by an onlooker, was played at the LECC in Sydney on Monday, showing the four officers holding the teenager on the ground and beating him 19 times with a baton.

In the recording, the teen, who for legal reasons can only be referred to as AO, can be heard yelling, "I'm not resisting!" to which one of the officers replies, "Yes you are, c--- give me your hand".

At another point, the victim shouts: "Someone please help me God. God" and also "f---ing hell, I'm not resisting but I want more water".

Earlier, counsel assisting the LECC, Terence Rowles, said when police arrived just after 2am they found the teenager naked, disoriented, and under the influence of drugs or alcohol.

In his opening address, Mr Rowles said the officers, who are set to appear at the hearing under the protection of anonymity, used OC spray, a taser, physical force and their batons on teen before transporting him into a police vehicle to Byron Bay police station.

The victim was then kept naked at the police station's holding dock for half an hour before being sedated and transported to hospital, the hearing was told.

Mr Rowles said AO, who later told authorities he had taken acid, appeared to pose no threat to the officers before being violently restrained, just after 2am.

"Although it is certainly the case that AO was acting irrationally and was plainly intoxicated in some way, he had not attempted to attack anyone, either physically or verbally. He was plainly unarmed," he told the hearing.

"There can be no doubt that because of his interaction with police, he was in considerable pain and his distress was exacerbated by his intoxication."

The teen suffered "extensive bruising" and a fractured rib in the altercation that developed after the officers were presented with "a difficult and unpleasant situation", he said.

A witness, codenamed W3, who watched the beating from his holiday rental balcony, said he had to avert his eyes at times during the ordeal.

"He (AO) was saying 'God help me, I need help' ... 'I need some water'," W3 told the hearing. "I was thinking, 'I hope this guy doesn't have a heart attack'."

The hearing continues before LECC Chief Commissioner Michael Adams.

EARLIER: A NAKED teenager beaten by four police officers in a Byron Bay laneway was in "considerable pain and distress" during the ordeal, a public inquiry into the incident has heard.

The Law Enforcement Conduct Commission, sitting in Sydney, is investigating whether four police officers caught on video detaining the 16-year-old in the early hours of January 11 this year used excessive force.

The confrontation near Nomads Backpackers Hostel, broadcast on national television soon after the incident took place, sparked community outrage on the NSW far north coast and calls for an official probe.

In his opening address on Monday, counsel assisting the LECC, Terence Rowles, said when police arrived in Lateen Lane just after 2am they found the teenager naked, disoriented, and under the influence of drugs or alcohol.

Mr Rowles said the officers, who cannot be named for legal reasons, used OC spray, a taser, physical force and their batons on the naked and unarmed teen before transporting him into a police vehicle to Byron Bay police station.

The teen, referred to by the pseudonym AO, remained naked in a police station holding dock for half an hour before being sedated then transported to hospital, the hearing was told.

Mr Rowles said AO, who later told authorities he took acid, suffered "extensive bruising" and a fractured rib in the altercation.

"There can be no doubt that because of his interaction with police, he was in considerable pain and his distress was exacerbated by his intoxication," Mr Rowles said.

"It is clear that when the four police officers arrived they were faced with a difficult and unpleasant situation.

"How they went about this task is the subject of this investigation."

The hearing, set to run for at least three days, was also played unedited mobile phone vision of the violent incident, showing the teen lying on the street screaming for help as police restrained him, hit him several times with batons, and demanded he comply with their instructions.

The hearing continues before LECC Chief Commissioner Michael Adams. - NewsRegional