This article was first published by RNZ.

It is one year today since the death of Baby Ru - with no one yet charged over the brutal attack that fractured the toddler’s tiny skull.

Wellington police still have six full-time investigators working on the case, and insist they are zeroing in on the person - or persons - responsible.

It is just eight minutes' drive to Hutt Hospital from Poole Street in Taitā - quicker if you are speeding, which we can assume one car was on this quiet Sunday morning, at about 10:30am.

The 20-year-old grey-green Nissan Sentra carried three adults and a little boy who was deeply unconscious, although his mother said later she could still feel his tiny heart fluttering.

Ruthless-Empire Souljah Reign Rhind Shephard Wall - since officially named Nga Reo Te Huatahi Reremoana Ahipene-Wall - died shortly after arriving at the emergency department.

‘Baby Ru’ was two days short of his second birthday.

Three ‘persons of interest’ remain the same

His mother Storm Angel Wall and her housemates Rosie Morunga and her partner Dylan Ross - who owned the car - were the only people in the house at the time he was injured.

According to police, they remain the only “persons of interest” in the case.

In an interview with RNZ, Detective Inspector Nick Pritchard said police were still determined to lay changes over the death.

“That’s been the aim from the beginning and that’s still our focus.

“We’re working for a one-year-old boy who can’t tell us what happened.

“There were three adults in the house when he suffered these injuries.

“Nobody has come forward from that group to accept responsibility. So we are working as hard as we can to piece together every strand of evidence to achieve that outcome.”

Within days of Baby Ru’s death, police confirmed the cause: blunt force trauma, either inflicted by a weapon or by slamming his skull on a hard floor or table.

At a media conference , Pritchard ruled out other causes - such as a piece of fabric tied around the little boy’s neck - and dismissed reports that he may have ingested baby wipes, which were found at the scene.

Pritchard said the investigation had “advanced a lot” in a year.

Six full-time staff were dedicated to the inquiry and had spent the year carrying out a large number of enquiries, interviewing witnesses, reviewing forensic evidence, carrying out search warrants and “continuously reviewing and reassessing the evidence”, he said.

Witness statements don’t stack up - police

The three persons of interest had all spoken to police and offered “varying degrees of cooperation”.

“Some things that have been said to police are inconsistent in terms of what the police have established in terms of evidence and facts,” Pritchard said blandly.

“So the door is still open. We would like whoever is responsible for this to come forward and tell us exactly what happened.”

It was not possible to simply charge three people with a crime “because they were there” when it happened, he said.

“In order to file charges under the legislation, we need to reach a certain threshold, the test for prosecution.”

In the weeks following his death, both Wall and Morunga posted on social media maintaining their innocence, while Wall has also given interviews to some media outlets.

Other members of the whānau have spoken publicly about their concerns for Baby Ru and attempts to alert the authorities.

In September, Morunga was sentenced to 18 months' jail on various charges, including theft and four assaults - one on a journalist, who was punched multiple times outside court during an earlier appearance.

Early on in the investigation, it was revealed that before police secured the scene, the car in which Nga Reo was taken to hospital returned to the Poole Street property three times and removed vital evidence.

This included a duvet cover, strap, hard drive and power back-up unit.

In February, Pritchard said police believed they knew who cleaned up the crime scene, but did not have enough evidence to charge anyone.

It was not known whether the items had ben destroyed or stashed somewhere.

Police were still keen to find the hard drive used to record CCTV footage from the house, he told RNZ this week.

Cop in charge ‘proud’ of team effort to date

When asked whether he had any regrets about the initial investigation - such as time it took to get a search warrant - Pritchard said he was “proud” of the team.

When police were notified by hospital staff of Baby Ruthless' unexplained death, it “triggered a sequence of events”, he explained.

At that stage, working on behalf of the coroner, they talked to hospital staff and family members to understand what occurred in the lead up to him being hospitalised.

“Then as those inquiries were completed, part of our investigation is to obtain a search warrant for the house.

“Looking back, I’m proud of the team effort, I’m proud of everything they did, and on the day [they] worked as efficiently as they could and on the basis of the information received.”

Experienced CIB investigators were used to dealing with serious crime, including homicide - but an investigation like this still took a toll, he said.

“Like anyone in society, seeing a crime like this where a defenceless one-year-old child has been subjected to violence by an adult or adults, it’s quite abhorrent and you ask yourself ‘How could this happen? How could someone do this to a defenceless young child?’.”

Even after a year, police were open to new information.

“Anyone who has any information, we would really like them to come forward and talk to us, no matter how small or insignificant they think that is.”

- RNZ