Police will not prosecute the engineers over the collapse of Christchurch's CTV building, which killed 115 people in the February 2011 earthquake. (Video first published in November 2017)

Families are disappointed an intense, three-year investigation into the Canterbury Television (CTV) building collapse has ended with a decision not to press charges.

Details of the decision emerged on Thursday when the Ministry of Business, Innovation and Employment (MBIE) told families in an email the prosecution would not got ahead.

The CTV building in Madras St, Christchurch, collapsed during the magnitude-6.3 earthquake on February 22, 2011, with the loss of 115 lives. Many others were seriously injured.

JOHN KIRK-ANDERSON/STUFF Detective Superintendent Peter Read and Canterbury District Commander Superintendent John Price discuss the police decision not to prosecute over the collapse of the CTV building.

Family members of some of the victims have pushed for accountability over the disaster. The police inquiry cost $1.18 million, including $1.15m in expert advice. Up to 13 staff worked on it at a time.

READ MORE:

* Special Investigation: Why did the building collapse

* CCTV building engineer Alan Reay still deeply anguished

* Dad: 'No accountability'

* What it was like for the CTV survivors

The email to families said police identified significant deficiencies in the CTV building design and considered charging Alan Reay and David Harding, the engineers responsible, with negligent manslaughter.

JOHN KIRK-ANDERSON The CTV building following the February 2011 Christchurch earthquake.

The evidence, however, failed to provided a reasonable prospect of conviction in court according to the Solicitor-General's prosecution guidelines, it said.

Maurice Gardiner, whose sister Donna Manning died in the building collapse, said it was somewhat surprising and disappointing no-one would be held to account.

"There was quite a bit of information leading towards prosecution .. then they turn around and say 'no'," he said.

KIRK HARGREAVES/STUFF CTV engineer Dr Alan Reay giving evidence at the royal commission of inquiry. Police considered charging him with manslaughter.

"All they [the victims] were doing was their jobs."

"There were fundamental flaws in the building ... I've always said I don't want a lynch mob, but certainly I don't want this to happen again."

Kendyll Lamont, who survived the building collapse, said she hoped for a different outcome, but accepted the police decision.

KIRK HARGREAVES/STUFF Engineer David Harding. Police considered charging him with manslaughter.

"I was just shocked and upset, blind sided really.

"After such a long investigation, they've done so much work ... I just assumed there would be a different outcome."

David Beaumont lost his son, Matthew Lyle Beaumont, a 31-year-old CTV programmer.

PHIL REID/FAIRFAX NZ The CTV building's destruction caused 115 deaths.

He was satisfied with no prosecution as there was "a whole series of neglectful people all the way through", not just a design issue.

A jury would struggle to understand the technicalities of the case, he said.

David Beaumont could not understand why the decision took so long.

SUPPLIED Donna Manning died in the CTV building.

"It's been a very difficult time and it wakes it all up again when things like this happen."

Justice Minister Andrew Little spoke briefly on the issue on his way into the house, but said he was not fully across the issue yet.

"Right now my thoughts are with the family," Little said.

JOHN KIRK-ANDERSON/STUFF David Beaumont's son, Matthew, died in the CTV building collapse.

"A bit like the Pike River families, they will be extremely disappointed that yet again, another tragedy, another disaster, that seems to have been avoidable, everybody involved seems to walk away scot-free."

"That's not right and I think we do have to do better."

He wouldn't rule out a law change as a result.

Iain McGregor / Stuff Kendyll Lamont was in the waiting room for Relationship Services when the earthquake hit. She survived.

CONVICTION WOULD BE 'DIFFICULT'

The documents show police wanted to charge Harding and Reay with manslaughter. Christchurch Crown Solicitor Mark Zarifeh believed the evidential sufficiency test was met by expert evidence from engineering firm Beca.

Deputy Solicitor-General Brendan Horsley disagreed.

SUPPLIED Jane Grant was nurse at The Clinic in the CTV building. Her husband, Murray, is "disgusted" no-one will be charged.

Horsley said for charges of negligent manslaughter, the Crown had to prove the conduct was so bad it deserved to be condemned as a serious crime. It would be difficult to show the conduct was one of the main causes of the deaths.

"A key difficulty for the prosecution would be in proving the CTV building would not have collapsed in the absence of the identified design errors," he said.

Another obstacle was the length of time between the design and when the deaths occurred.

SUPPLIED Rhys Brookbanks perished in the CTV collapse. He is pictured here with his fiancee, Esther Jones.

"The Crimes Act requires death to have taken place within a year and a day after the defendants' negligent conduct ceased . . .On the most natural interpretation of events the alleged negligence ceased when the design process was complete, in 1986. The year and a day rule is an historical anomaly and law reform is currently being considered."

In the email to the families, Detective Superintendent Peter Read said he knew the decision would cause disappointment.

"The evidence and findings of the Royal Commission are not in themselves sufficient to meet the test for prosecution, even with the further information gathered during our investigation."

Joseph Johnson Detective Superintendent Peter Read.

His message to the families was: "I understand this will be a very difficult day for you. I would like to again extend our deepest sympathies to all of you who lost loved ones in the CTV building."

A royal commission of inquiry found the CTV building had serious design flaws and should not have been granted a building consent.

Its report said engineer David Harding, who designed the building in 1986, was left largely unsupervised by his boss, Alan Reay, despite Harding's limited experience designing multi- level buildings. Harding was working "beyond his competence" and Reay did not review the design, the report said.

IAIN MCGREGOR/FAIRFAX NZ Search and recovery at the CTV building after the February 22, 2011, earthquake struck Christchurch.

'THERE IS NO CLOSURE'

Murray Grant, who lost his wife, Jane, a practice nurse at The Clinic in the CTV building, said the decision was "not right".

"There should be a prosecution over it. I've always said it."

"I'm very disappointed, I'm quite disgusted, it's just not right that such a catastrophe can happen and the people involved can get away with it."

Fran Brookbanks' son, Rhys, 25, was CTV reporter and perished in the building collapse.

She was not surprised by the decision not to lay criminal charges, but had wanted someone held accountable.

"The stress of going through that prosecution. I don't think I'd be able to go through that."

"To dig it all up again, I would find that quite hard."

She now lives in Auckland and finds going to Christchurch difficult.

"It's something we haven't got over. Rhys was our only son, we have a daughter, it was her only brother.

"There is no closure. The pain is just something you have to live with. We watch our son's friends grow older get married have children, for us that will never happen."

"You learn to live with the pain, but it doesn't get any easier."

WHAT WENT WRONG

Design: Structural engineer David Harding, of Alan Reay Consultants, was given the CTV assignment in March 1986. He had limited experience designing multilevel buildings, but was left largely unsupervised by principal Alan Reay.

The Canterbury Earthquakes Royal Commission found there were non-complying aspects of the design because Harding was working "beyond his competence" and Reay did not review the design. This led to a building design that was "deficient in a number of important respects", the report said.

Consent: Christchurch City Council consenting officer Graeme Tapper had misgivings about the structural integrity of the design, but no record of his concerns being addressed exists. Tapper told his wife he felt pressured by council chief engineer Bryan Bluck to approve the permit in September 1986.

The commissioners found it was likely Reay convinced Bluck that concerns about the design were unfounded. The permit should not have been issued because the design did not comply with building bylaws, the report said.

Construction: Williams Construction, led by managing director Michael Brooks, construction manager Gerald Shirtcliff and foreman Bill Jones, began building work in October 1986. The Royal Commission found Jones was competent but lacked supervision and that Shirtcliff did not spend enough time on site.

Defects were identified after the collapse, including the lack of roughening of joints and reinforcing bars in precast beams not conforming to design. The report said this should have been visible to the engineer, foreman and construction manager.

Retrofit: In January 1990, Holmes Consulting Group prepared a structural report for a potential buyer that noted a "vital area of non-compliance" in the tying of floors to shear walls and that the building could separate from the shear core in a quake.

Holmes recommended remedial work, including steel drag bars on all levels above the ground floor. The bars were installed in November 1991, but only on levels four, five and six, and no permit was sought. The commissioners found the identification of that should have signalled the need for a more detailed review of the design.

Inspection: The building was green stickered after the September 2010 quake. Building manager John Drew employed structural engineer David Coatsworth, who assessed it as safe.

Coatsworth asked for structural drawings, but did not get them in time. His recommendations for further assessment were not carried out. A rapid assessment was done after the Boxing Day quake in 2010.

The commissioners found Coatsworth could have clearly explained the "nature, extent and limitations" of his assessment.

TIMELINE

1986: The CTV Building is designed by Christchurch engineer Alan Reay's firm and granted building consent.

January 1990: Holmes Consulting Group prepares a building structural report for a potential purchaser. Engineer John Hare identifies ties between floors to the north shear wall are non- compliant with the building code.

December 1990: Madras Equities buys the building and leases it to ANZ Bank.

1991: Steel bars are installed by Alan Reay's firm on legal advice to deal with connection issues.

2008: Kings Language School leases the fourth floor of the building.

September 4, 2010: Magnitude 7.1 earthquake shakes Christchurch and damages a raft of buildings in the central city.

September 29 2010: Engineer Geoff Coatesworth completes detailed inspection of the building, concluding no evidence of structural failure exists.

December 27 2010: After the central city is again shaken by an aftershock, the CTV building is again inspected and given a green sticker.

February 22, 2011: The CTV Building collapses during a 6.3 magnitude earthquake, killing 115 people.

December 2012: The Canterbury earthquakes royal commission finds David Harding was working "beyond his competence" in leading the CTV building design.

July 2014: The Institution of Professional Engineers New Zealand (Ipenz) holds two disciplinary hearings into Harding's engineering activities despite him having resigned as a member of the industry body days earlier.

September 2, 2014: Police announce they will further their investigation into the building collapse.

September 17, 2014: The High Court rules the findings of Ipenz disciplinary proceedings against Harding should be made public.