Royal commissions of inquiry now under way into the Christchurch earthquake damage and the Pike River mine disaster are starting to bear fruit.
In Christchurch, a report to the commission by the Department of Building and Housing finds the Canterbury Television building that collapsed in the February earthquake, killing 115 people, failed to meet the building code when constructed in 1986. At Greymouth, the Pike River inquiry has been given a reasonable guess about how the explosion happened.
The Pike River commission is working under the considerable disadvantage that the mine remains sealed and nobody can investigate the scene of the disaster.
It is having to deduce what may have happened from records of mine operations and the testimony of miners, including the two who got out that day.
Since the pair did not feel a shockwave, experts conclude the first explosion on November 19, 2010, occurred deep in the mine workings. They have also found a crucial gas sensor to be in a state of disrepair and poorly positioned.
Records of gas readings two and four days before the explosion differed between sensors that were not far apart, suggesting they were were not being calibrated and maintained properly.
The design of the mine, with just one entrance and a ventilation shaft, suggests it would have been difficult to keep air circulating. That suspicion is strengthened by an unusual positioning of the main underground fan and the state of screens used to direct air into tunnels.
When it comes to the cause of the gas build-up and explosion, the inquiry is relying on conjecture.
The best guess of the experts is that a recently mined area may have collapsed, sending volatile methane through the mine. The methane could have exploded when water pumps were turned on, producing an electric spark.
Meanwhile at Christchurch, the Building and Housing Department's report has been referred to the police for possible criminal investigation.
The department's inspectors found the CTV building's concrete columns were brittle and walls crucial to its stability were not symmetrical, causing it to twist more than it should under the stress of a 6.3 magnitude earthquake, let alone the ground acceleration forces unprecedented in New Zealand that hit Christchurch that day nearly a year ago.
Naturally every word of evidence to the royal commissions is painful for families of the victims to hear, but necessary for them to hear it, too.
Human nature desperately needs answers to how and why loved ones have died, if answers are possible. The temptation to cast blame is difficult to control.
With hindsight it usually becomes clear that there are things people could have done, or could have done better, that might have saved lives. It is only fair to these people that hindsight is put to one side and their actions, or lack of them, are assessed against what could reasonably be expected of someone in their position at the time.
What procedures were routinely followed? Was anyone wilfully reckless or knowingly putting lives at risk for the sake of saving some money?
It is as well that royal commissions do not have powers to find people guilty of actions or neglect that might amount to a criminal offence. The police can make that decision outside the emotions and pressure of a public inquiry.
Those who know lives might not have been lost if they had acted differently, know it now and will live with it for the rest of their lives.
Royal commissions are less about blaming individuals than drawing lessons that might help save lives in the future. That needs to be kept in mind as the evidence unfolds and the tragedies are relived.