CHRISTCHURCH, NEW ZEALAND (WASHINGTON POST) - The man accused of carrying out the twin massacres at New Zealand mosques in March will become the first suspect charged under the country's anti-terrorist laws passed after the 9/11 attacks.

The decision will be closely watched around the world as a test of bypassing regular criminal statutes for an apparent hate crime and opting for terrorist charges, which opens the door for examinations of ideology and political motivations during the trial.

Critics say a prosecution case based on "engaging in a terrorist act" would add no more years to the possible sentence for the alleged gunman, 28-year-old Brenton Tarrant.

Instead, they argue, it could potentially allow him to use the trial as a platform for white supremacist views and other extremist beliefs - which would challenge efforts by New Zealand's prime minister, Jacinda Ardern, to keep the spotlight away from the suspect and his views.

The Australia-born Tarrant is expected on Friday (June 14) to enter a plea for the March 15 slayings, which claimed 51 lives in the deadliest mass shooting by a lone gunman in New Zealand history.

Tarrant - who appeared in court in April - was determined fit to stand trial after a mental health assessment. He plans to represent himself at the trial, whose date has not been set.

On Friday, Tarrant is expected to issue his plea through lawyers and will not attend the hearing at Christchurch's High Court, appearing via audiovisual link from Paremoremo prison in Auckland.

If Tarrant enters a plea of not guilty next week - as indicated in a manifesto posted online before the killings - it potentially opens the way for a self-defence case that could dive into his hateful outlook. His writings included anti-immigrant and anti-Muslim diatribes.

On the day of the mosque attacks, Ardern said the incidents could "only be described as a terrorist attack". New Zealand's Parliament later voted to ban military-style semi-automatic weapons.

Tarrant was initially charged with murder and attempted murder counts. On May 21, however, Police Commissioner Mike Bush said prosecutors will "allege that a terrorist act was carried out" in the Christchurch attacks.

Alexander Gillespie, a law professor at the University of Waikato, told The Washington Post that "motives are not hugely important" when prosecuting someone on murder charges.

"You just have to prove that the accused had an intent to kill," he said.

But terrorist charges opens up different paths for both the prosecution and the accused.

"The prosecution is drawn into the business of ideology and political views and so on, which make their work a lot harder potentially," Gillespie said.

"The risk of this is that you end up potentially giving the accused a platform to try to justify his actions," he added. "Terrorists seeking notoriety crave these types of chances, as a few sound bites could echo around the world as quickly as his live-streaming of the actual killings."

New Zealand's Suppression of Terrorism Act 2002 - passed through Parliament during the worldwide fallout after the Sept 11, 2001, attacks - requires the prosecution to prove that the defendant intended to kill for a political, religious or ideological purpose.

Only once before have the police attempted to deploy the law. In 2007 a group was arrested after allegedly engaging in paramilitary-style training with semi-automatic weapons in a remote area of New Zealand's North Island.

David Collins, then-New Zealand's solicitor general, ruled that there was insufficient evidence to justify charges under the legislation, which he characterised as "incoherent and unworkable".

It is not yet clear whether international publications will be allowed to report from the courtroom when Tarrant's trial takes place. But a group of leading domestic media organisations have voluntarily signed a pledge to avoid amplifying "white supremacist and/or terrorist views or ideology" that the accused may attempt to promote.

Under New Zealand law, judges have broad discretionary powers to control the conduct of any hearing. This allows for the possibility of journalists in attendance being asked to censor their reporting at the trial.

On his first and only appearance in person before a court since the attacks, Tarrant made a hand gesture associated with white nationalism.

"The Muslim community has clearly stated its wish to leave all decisions in relation to charges and the trial to the relevant authorities and to let the judicial process take its course," said Jamaal Green, a spokesman for the Christchurch Muslim community.

When asked about the implications of the terrorism charge, a police official directed The Washington Post to a news release issued last month, adding: "As the case is before the courts no further commentary on the charges will be made by Police, Crown Law or the Christchurch Crown Solicitors Office."

Despite the complications, the law professor Gillespie expressed the view that "there are good reasons to also try this charge."

"First, if the law is on the books, it should be auctioned. Second, if it was ever going to fit, this is the time," he said. "Finally, and perhaps most importantly, sometimes you need to add a charge that reflects the social repugnance of a crime of this nature, which goes beyond normal legal considerations."