Samuel Timothy Brown was only 20 years old when he died after being found on the side of the Gold Coast Highway with severe head injuries in the early hours of November 25, 2012.

How Sam Brown got those injuries remains a mystery more than five years on.

A second inquest is now being held in the Coroner's Court at Southport.

Sam Brown was described as happy, the life of the party, and an animal lover by family friends in court.

The long-haired care-free man was a keen footballer for the Burleigh Bombers.

He used to give up his weekends to coach U10's football teams for the club.

His mother Leanne Brown said Sam loved his sport, his club and always had a lot of friends.

She said he never argued and was a happy and relaxed young man.

Beers, a barbecue and a 22nd birthday party

Sam's older brother Nick Brown has been best friends with Josh Searle and Robert Cosgrove since year seven.

Sam Brown was described by family friends as a man who 'loved his sport'. ( Supplied: Brown family )

The Searle family testified it was Josh's 22nd Birthday party that night, and that he and 10 friends were having beers and barbeque out the back of Josh's parent's place.

Sam Brown came along at about 9:30pm after attending a football function.

About midnight everyone went home, or went to sleep on the mattresses Christina Searle (Josh's mum) had provided.

But Sam decided to go out with his older brother's friend Robert Cosgrove.

Christina Searle told the inquest she offered to drive the boys, but they turned her down, saying they would catch the bus.

The inquest was shown a video from a bus security camera.

The boys are denied access as they were visibly intoxicated and carrying a bottle of rum.

The lies and deceit of a friend

Robert Cosgrove's account of the night is told through the smoke screen of high intoxication levels and the influence of MDMA.

In his original police statement, Mr Cosgrove said the pair decided to walk to Broadbeach after being kicked off the bus, and that he lost sight of Sam Brown during the walk.

His first statement suggests he backtracked and looked for Sam but couldn't find him, so he took a taxi to Broadbeach to look for him before returning to the Searles' place.

Sam's friend Robert Cosgrove admits to lying in his former statements. ( ABC News )

This is the story Josh Searle's parents testified Robert had told them that night.

But Mr Cosgrove told the inquest that was a lie he made up because he was ashamed of his actions.

He said he was "riddled with guilt" as he intentionally left a drunk mate behind on the side of the road.

Mr Cosgrove was presented with texts he sent a girl on a dating website, which said "he felt like crap" because he ditched his friend to meet up with her.

"I think I wanted to go do something else," Robert Cosgrove said.

"Read back at those texts it makes sense, but I don't remember the point in time."

Robert Cosgrove also admitted to the inquest that he had used a fake name on the dating website because he had a girlfriend at the time.

The name he used was Nick Brown — the name of his friend and older brother of Sam Brown.

After this revelation there was dead silence in the inquest, until the real Nick Brown angrily stood up in the public gallery.

"You're f---ing kidding me," he said as he stormed out.

"What has our family ever done to you?" mother Leanne Brown exclaimed.

The mystery of Sam's final hours

Robert Cosgrove admitted leaving Sam Brown on the side of the road as he went to Broadbeach, supposedly to meet a girl.

He indicated Sam was drunk but uninjured when he left.

Mother Leanne Brown said Sam had never taken drugs and his toxicology report showed there weren't any in his system when he died.

After Robert leaves the time frame gets a little sketchy, as the first responder do not remember exactly what time they found Sam.

But at approximately two in the morning a group of people returning from a night out in Surfers Paradise find Sam Brown lying on his back on the side of the road.

Luke Pascoe and Allan Baker were among them.

The saw Sam while stopped at a red light, they instructed the taxi driver to do a U-turn.

Luke Pascoe told the inquest they got out of the taxi and headed over to the man.

"He was making noises, blood was gushing out of his head," Mr Pascoe said.

"He definitely wasn't well.

"Blood was dripping down the road and into the gutter."

One of Luke's friends called an ambulance.

Sam Brown was found lying on his back with severe head and facial injuries. ( ABC News: File )

Taxi driver Ezabell Hannah was also one of the first on scene.

She told the court she was driving south on the Gold Coast Highway at about 1:50am on the 25th of November.

Ms Hannah said she saw a group of people shouting and arguing on the northbound side, but continued driving as she had people in the taxi.

After dropping off her customers she drove north on the Gold Coast Highway at about 2:30am, when she saw someone lying on the road.

"I can't remember exactly the time," she told the inquest.

"He didn't respond when I beeped the horn, so that's why I stopped.

"I went down to seeing what going on, I found the person with a lot of blood."

Injuries inconsistent with a car strike

Police initially suspected a hit and run, with the first responding police officers testifying they treated it this way.

In 2015 police charged a taxi driver with 'failing to stop at a road incident'.

Those charges were dropped due to a lack of evidence.

The lead forensic crash investigator said he did not agree with this charge from the outset, and indicated in his report that Sam Brown's injuries weren't consistent with a car strike.

Steven Cornish was based at the Coomera Serious Crash Unit and was woken with a call asking him to come to the scene.

He told the inquest there was no car debris surrounding the blood stain which marked where Sam Brown had been.

"When someone is hit by a car, 99 per cent of the time there is debris, glass fragments, broken lights, paint or plastic cracks from bumpers," Mr Cornish said.

"And we located nothing…[there were] no tyre friction marks.

"Nothing in the direct vicinity of Sam."

Police comb the scene for evidence on November 25, 2012. ( ABC News: File )

Senior Constable Cornish said Mr Brown's injuries were not like other pedestrian strikes he had seen.

He said usually when someone is hit by a car they suffer broken legs and pelvic injuries from the impact and flipping over or off the vehicle.

If the person was lying down, they would likely suffer crushing injuries and be marked by the tyres.

"[Mr Brown's] legs and feet and clothing were scuff free from the torso down," said the investigator.

This is a view repeated by one of the first attending paramedics.

Jason Harris testified at the inquest Sam Brown's injuries were "too neat" to have come from a car strike.

"There was quite a fair bit of blood," he said and referred to the head injuries including a cut under the chin.

But Mr Harris said the clothing "didn't look terribly disturbed" and was "too neat for a classic sort of car accident".

When questioned on his expertise to voice this opinion by the counsel assisting Queensland Police, Mr Harris said he was not an expert, but this is his simply his personal opinion based on attending a number of pedestrian accidents.

No chance of survival

Gregory Comadira, a critical care doctor at Gold Coast University, told the inquest that although Sam Brown was still alive when he arrived at hospital, his injuries were catastrophic.

"A large thing or a force has hit and the head and it has stopped quickly, but the brain is still going," he said.

"It is a significant high-speed injury.

"In this case the whole brain has been shattered."

Loading

When pushed on what could have caused such an injury Dr Comadira cautiously ruled out a car strike.

"That's enough force to cause these injuries, but would that cause other injuries? I would expect so — limb injuries because they are the right height for a bumper bar.

"We would have expected to see abdominal injuries, but they are not there," he said.

Dr Gregory Comadira said a strike from a fist or a hammer would have caused localised trauma to an area of the skull and brain.

In this case the entire mass was affected.

He also said Samuel Brown didn't just simply fall over in his drunken state.

"These aren't low speed injuries…it's more than just falling over," he said.

The inquest has been adjourned until the 21st of May.