It was a scoop that led all the way to the High Court.

Key points: The AFP raided News Corp political journalist Annika Smethurst's Canberra home in June 2019

The AFP raided News Corp political journalist Annika Smethurst's Canberra home in June 2019 Lawyers have challenged the validity of the warrant used by police

Lawyers have challenged the validity of the warrant used by police The raids on Ms Smethurst and on the ABC, over a separate series of stories, prompted a broader debate about press freedom

This morning, News Corp journalist Annika Smethurst will find out if the High Court is prepared to throw out the warrant used to search her home in June last year.

In April 2018, Ms Smethurst published stories suggesting the Department of Home Affairs and the Department of Defence were discussing a plan to expand the powers of the Australian Signals Directorate (ASD) to secretly access data in Australia as well as overseas.

The Federal Government said the story misrepresented discussions, but later the Home Affairs Minister Peter Dutton conceded there was a plan to expand the agency, to target child sex offenders.

Two of the stories included images of a document created by ASD, marked 'secret' and 'top secret'.

More than a year later, Australian Federal Police (AFP) officers knocked on Ms Smethurst's door with a search warrant, alleging that she and the Sunday Telegraph had breached the 'Official Secrets' law in the Crimes Act.

Ms Smethurst has never been charged with any offence, and the warrant only includes a general list of items, with an order she provide her phone password.

The key question before the High Court was whether the warrant was valid.

Lawyers for Ms Smethurst identified several flaws, including that it did not specify the crime, and the law it was issued under was invalid because it breached the implied constitutional right to freedom of political communication.

But lawyers for the Federal Government told the court it was enough to identify the kind of offending, and a warrant did not have to specify a charge.

Another key flashpoint was whether, if the warrant was invalid, the material collected by the police should be destroyed or handed back.

Court documents reveal some data was copied from Ms Smethurst's phone, but nothing else was taken from her home.

The Federal Government has asked to be allowed to keep the material in case of any future prosecutions, even if it was illegally obtained, something that was strenuously resisted by Ms Smethurst's lawyers.

Raids prompted broader political debate over national security

Political journalists campaign for the public's right to know outside Parliament House on 21 October 2019. ( ABC News: Toby Hunt )

The AFP raid on Ms Smethurst's home in June 2019, and another raid on the ABC's Sydney headquarters the following day, prompted a broader debate over press freedom.

Media companies put aside their usual fierce competition, joining forces to lobby the Federal Government for greater protections for journalists and whistleblowers.

The Right To Know Coalition, as it has been called, has argued too much ground has been ceded in favour of national security, undermining the media's freedom to hold the Government and its agencies to account.

Two parliamentary inquiries were established — the Federal Government asking Parliament's powerful intelligence and security committee to investigate the matter, along with a separate Senate probe launched by the Greens.

During the debate, and as the AFP investigations continued, Attorney-General Christian Porter announced police and Commonwealth prosecutors would need his permission to charge and take journalists to court.

Rather than easing concerns about journalists being pursued, lawyers raised fears it would put even more pressure on the media to keep the Government onside with its reporting.

The AFP has denied suggestions the raids were designed to intimidate journalists and whistleblowers, but has admitted the matter could have been handled better.

The ABC unsuccessfully challenged the AFP search warrant over documents which led to its stories, known as the Afghan Files, in the Federal Court earlier this year.

The ABC said it would not challenge the ruling, as it did not believe litigating its way to "reforming fundamentally bad laws" was the best approach, urging politicians to do that work instead.