A small but vocal crowd of Julian Assange's supporters stood outside the court chanting messages of support.

Key points: Assange wanted in US on 18 criminal counts including hacking and espionage charges

Assange wanted in US on 18 criminal counts including hacking and espionage charges US government says he put lives at risk by publishing documents

US government says he put lives at risk by publishing documents Defence team argues Assange will not get a fair trial in US, is a suicide risk

Inside Court 2 at the Woolwich Crown Court, Assange himself spoke of his struggle to hear proceedings above the noise his loyalists were creating.

After nearly a decade in some form or another of captivity, it would've provided some solace for the WikiLeaks founder, that his diehard supporters are still there.

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Judge Vanessa Baraitser acknowledged it was not in her jurisdiction to stop the protest and so the first day of the extradition hearing went on, with a dull rumble seeping through the walls.

Assange sat throughout the hearing behind a glass panel, seated between two security guards.

Dressed in a grey suit, grey jumper and white shirt, he looked calm throughout, eyes forward, as the US legal team and then his defence outlined their opening arguments.

The US vs Julian Assange was underway.

It is not a trial to determine his guilt or innocence of the 18 charges he faces – the judge needs to decide only if there are legal grounds for the 48-year-old to be sent to the US to face trial there.

Even then, after an appeals process that could take years, the Government of the United Kingdom will make the final decision on whether they're willing to send the Australian to America.

A mask-wearing supporter of Julian Assange outside Woolwich Crown Court. ( ABC News: Tim Stevens )

The case against Assange

After the initial hearing, it is clear lawyers for the US Government will argue the case for extradition on two broad fronts.

One; that Assange simply broke the law by allegedly conspiring with former US Army intelligence analyst Chelsea Manning to hack a US Department of Defense computer.

Supporters chanted "free free Julian Assange". ( Reuters: Hannah Mckay )

And, two; that he went on to publish thousands of classified documents that put the lives of US informers at risk, some of whom have subsequently disappeared, and may have damaged the war against terror and the security of American citizens in doing so.

"What Mr Assange seems to defend by freedom of speech is not the publication of the classified materials but the publication of the names of the sources, the names of people who had put themselves at risk to assist the United States and its allies," James Lewis QC, lawyer for the US, told the court.

Some sources identified by WikiLeaks "subsequently disappeared" Mr Lewis said, although he added US authorities could not prove that was a result of WikiLeaks' action.

Assange 'a suicide risk if extradited to US'

The Defence will be driven by politics and process.

Assange's lawyers will drive home President Donald Trump's dislike of the press, and argue he wants to use Assange as an example in his war against "leakers and journalists".

And, the supposed promise of a presidential pardon from the Trump Administration – delivered by a former US Congressman in 2017 — will also form part of the case.

Some pro-Assange protesters camped in tents overnight ahead of the extradition hearing. ( ABC News: Tim Stevens )

The White House flatly denies it – but as Counsel for Assange, Edward Fitzgerald QC, remarked today, "He would say that wouldn't he?".

When it comes to process, they'll point to the illegal surveillance of the Ecuadorian embassy and argue Assange can't receive a fair trial as conversations with his lawyers were listened to by spies from the US.

They'll even present an anonymous witness, known as Witness 2, who will allege the Americans discussed kidnapping or poisoning Assange.

And they'll argue if Assange is sent to an American prison it would expose him to a very high risk, if not certainty, of suicide.

The interest in the case is huge, not least because it's the first time the United States Government has charged a journalist – that Assange's team argues he is – or a publisher, under the 1917 Espionage Act.

He faces 17 charges of Espionage and one count under the computer Fraud and Abuse Act, in relation to one of the largest compromises of classified material in US history.

Supporters chanted slogans outside Belmarsh Magistrates Court in London. ( AP: Matt Dunham )

Lawyers for the US described as "hyperbole" that Assange could be jailed for 175 years if found guilty, but each espionage charge carries a maximum 10-year prison sentence.

A maximum of five years goes with the hacking charge.

Assange raised a clenched fist to supporters in the public gallery as the day's proceedings ended before being returned to his cell in the adjacent Belmarsh prison.

He'll appear in person on each of the five days of the initial hearing this week, but his lawyers have now made it clear its very unlikely he will testify.

Witnesses will begin giving evidence in mid-May.