The mother of a man accused of threatening to carry out attacks on two Auckland schools and destroy public buildings changed her story about where her son lived.

Tiedan Huo is on trial in Manukau District Court, where it is alleged he threatened to kill students and staff at Waiuku and Rutherford colleges, and to damage or destroy two police stations and Parliament buildings.

He is also charged with unlawful possession of a firearm and of explosives, and possession of objectionable material.

The charges stem from a manifesto, which it is alleged Huo distributed in another person's name early on the morning of 12 March last year.

Huo denies the charges.

The court heard evidence that his mother Pengxiao He told police in a statement in March last year that it was her son's bedroom in which a firearm had been found at the Waiuku farm.

But on Tuesday she told the court that her son had not been living at the property and that she had felt pressured into giving that statement.

"I was forced because they asked me to do a statement, I said I don't want to...but they said if I didn't do a statement they would arrest me right now, immediately."

Crown prosecutor Gareth Kayes asked Ms He about those inconsistencies.

"Ms He that's simply not true is it, you weren't forced to say any of these things were you," he said.

"In your [police] statement you said Tiedan has a room at [the address] it is the one closest to the living room," Kayes said.

"I suggest you are lying now because you know a firearm was found in that room and you don't want Tiedan to be in trouble," he said.

Ms He objected and said a former tenant had visited, staying in that bedroom.

During a search warrant at the Waiuku farm last March, officers located a blueprint diagram for a military-style AR-15 rifle in a bedroom they had been told was Huo's. It was the type of firearm used by the Christchurch terrorist.

They also found a loaded pump-action shotgun on the bed, as well as 96 shotgun cartridges.

A box containing a further 250 cartridges was found in the living area.

Police also located a 3D printer, firearms parts, a machete, a knife, and multiple spent shotgun cartridges.

Ms He had a gun license to keep firearms, but this was revoked within days of her son's arrest.

Earlier on Tuesday, Ms He told the court she was not computer literate and had given her son access to her email passwords and her credit card.

She said she had not seen him with any of the firearms or knives that were found.

Kayes asked Ms He to view a list of items, including weapons, bought from AliExpress with her credit card.

"We will hear evidence that someone purchased a hunting bullet shell bag, military gear... was that you?," he said.

"Someone has purchased a Super Stabby bayonette, that's a knife... was that you?"

Ms He said she had not made those purchases and bought the two firearms she owned under licence from Gun City to shoot ducks on the farm because they are a pest to her market garden.

She said she had bought a 3D printer when her son asked her to and they had made a cat and a buddha statue.

The threatening email

The manifesto was purportedly emailed by a female former Waiuku College student, but after she allowed police to examine her electronic devices, officers established this was not the case and their inquiries led them to Huo.

The threatening email was sent via an encrypted service, but police found a screenshot on Huo's laptop captured just minutes after it was sent, showing the same username as the email.

It set out in some detail the preparations the sender said they had made to carry out attacks on Waiuku and Rutherford colleges, as well as damaging the Pukekohe and Te Atatu police stations and buildings at Parliament.

That included making firearms using a 3D printer and creating bullets and explosives to be used in an attack.

The sender said they wanted to kill more people than the Christchurch mosque terrorist, who murdered 51 innocent people on 15 March 2019.

The former student whose name was allegedly used as the email's sender had lived at the Waiuku farm with her father as a tenant of Ms He's.

Ms He said her son knew her.

"The kids knew each other because [the tenant] was hoping that his daughter would develop a relationship with my son to help his daughter to gain residency but my son refused."

The trial before Judge Sanjay Patel has been set down for two weeks.