Police knew that the use of elite armed officers in the raid on Kim Dotcom's mansion would come in for heavy public criticism, but chose to put safety ahead of "bad PR", it has been revealed.

The head of the New Zealand arm of the operation against the alleged internet pirate was grilled on the stand at the High Court at Auckland for more than five hours yesterday, in what turned into a fierce battle of wit against one of the country's top defence lawyers.

Detective Inspector Grant Wormald, the head of the Organized and Financial Crime Agency (OFCANZ) laid out step-by-step the reasons the elite police squad, the Special Tactics Group, were brought into help with the January raids.

Wormald said in planning the raid there were three objectives - to safely execute search warrants, to secure evidence and to arrest and search those on the property.

Balanced against that were the risks - the biggest of those including the loss of evidence if suspects weren't detained immediately, the fact there were firearms on the property, the potential for "over-zealous" intervention from security staff, and a fleet of suped-up cars which provided a means of speedy exit from the property.

Police were also extremely mindful that there was a pregnant woman and several children on site at the "extensive" grounds which provided added complications.

All of those factors led to the belief that a helicopter was needed in the raids.

The only police officers trained to work with helicopters were the STG, Wormald said.

"When you put all of the material together and look at all of the circumstances and all of what we wanted to achieve... the very best resource that New Zealand police had to achieve our goals...were the STG staff."

He said he knew there would be a feeling from the public that it was "over-the-top" to use the STG and the helicopter but ultimately, he was responsible for police and public safety and that did not outweigh the risk of bad PR.

Dotcom's lawyer, Paul Davison, QC, unpicked each argument with methodical tenacity, saying that police safety came at an "enormous cost" to his client's rights and privacy.

"[Police] are not every day going into domestic houses armed to the teeth with automatic weapons... in a paramilitary fashion...shouting orders at each-other and shouting orders at those in the household ....[and] treating everyone as detainees," he said.

"Or have I missed something?"
Wormald replied: "I think you have missed something."

"Every time we do a search warrant we do a risk assessment and if in that assessment there are firearms on the property we will not execute a warrant without armed police being present," he said.

"We do search warrants in domestic houses every day. Often there are women and children present. It's just part of doing the business that we do."

The hearing continues today.

- © Fairfax NZ News