Waikato expressway attack: Three months, 25 witnesses, zero arrests - why has no one been charged?

It's been three months since a motorist pulled over and was viciously attacked after being swarmed by members and associates of the Tribesmen gang on the Waikato Expressway.

The assault on March 11, in front of at least two dozen drivers, critically injured a 31-year-old victim.

At the time one witness recalled: "There was a gentleman on the ground, his face covered in blood. He was lying on his back and his shirt was off and his pants were half down. I thought he had passed away, he looked lifeless. It was terrible."

A source alleged one of the riders linked to the Tribesmen was clipped by the man's ute - and when the vehicle's occupants stopped to check on the rider they were brutally attacked.

Now, after three months and witness interviews - and video footage of the brutal attack - there have still been no arrests or charges laid.

A convoy of about 70 motorbikes were trailing the red ute on the Waikato Expressway when a man was attacked after pulling over. Photo / Supplied

When approached by the Herald, police said: "the investigation is still under way".

Police did not answer a question about what complexities authorities were facing that may be preventing those responsible from being charged.

The last update on the victim's condition was in April when police said he remained in hospital in a stable condition.

No further update has been provided.

Witness footage has revealed Tribesmen gang members driving recklessly on the Waikato Expressway before a violent assault on a man. Photo / Supplied

The complexities police face

Speaking to the Herald in April, former police officer Lance Burdett said while there was clear footage of the attack, the investigation was unlikely to be straightforward.

"Because it's a gang involved it might get people to second-[guess] if they were going to report something.

"It's happened before where witnesses have been threatened or intimidated."

One witness revealed they felt intimidated after being approached by the gang.

Before the attack, they said they had noticed how "aggressive" and "wild" the group was behaving - and started recording.

Soon afterwards and in a panic, they dropped their phone when they were greeted at their car window by one gang member who had indicated they'd seen them recording.

Burdett explained the initial phase of the investigation would involve scene examinations to gather forensic evidence such as weapons, identifying objects and fingerprints.

Detectives would broaden their investigation to covert tactics and police squads dedicated to organised crime would be pulling together intelligence they had on the gang.

If they are able to, they would also liaise with criminal informants within the gang scene who may have details, Burdett said.

It is understood members of the Tribesman gang were involved in the attack. Photo / File

When detectives were able to obtain sufficient evidence they'd be able to seek search warrants to go into gang-related establishments.

"They will want to make sure that the information is authentic and with gang involvement in particular you have to build a case - you build a case first before you go and speak to the people, it doesn't matter who it is," said Burdett.

Police may then be able to use a search warrant to gather supporting evidence.

University of Canterbury gang expert Jarrod Gilbert also weighed in and explained why dealing with gangs added another level of complexity, and noted they were all wearing helmets.

Gang members often operate with code of silence and will not dob in anyone or provide any information that might assist police.

Burdett added that the entire investigation could take up to a year but through covert and overt means of gathering information, detectives will eventually identify suspects.

Burdett said the person or people of interest would be spoken to last.

"They'll be wanting to make sure they have sufficient evidence and enough witnesses until they make that final move," he said.

"As a general rule you only get one shot at this and the chance is that the person isn't going to say anything, but that doesn't matter at that point if [police] have enough information."