Hundreds of people including Roger Waters, co-founder of the Pink Floyd rock group, and designer Vivienne Westwood, marched through central London on Saturday demanding that jailed Wikileaks founder Julian Assange be released.
He denied Assange was facing the charges because he had published "embarrassing" information the U.S. would rather was not disclosed.
The extradition hearing follows years of subterfuge, diplomatic dispute and legal drama that have led the Australian computer expert from fame as an worldwide secret-spiller through self-imposed exile inside the Ecuadorian Embassy in London to incarceration in a maximum-security British prison.
WikiLeaks was founded in 2006 but came to prominence in 2010 when it published a classified video showing a United States military helicopter killing around 12 people, including two Reuters journalists.
Britain's Crown Prosecution Service says the court must also weigh whether "extradition would be disproportionate or would be incompatible with the requested person's human rights". He's accused of working with former Army intelligence officer Chelsea Manning to get classified documents from databases containing about 90,000 Afghanistan war-related activity reports, 400,000 Iraq war-related reports and 250,000 State Department cables.
"We are preparing for a case that the world superpower has had 10 years to prepare for", Jen Robinson, one of Assange's lawyers, said at a panel discussion earlier this month.
Protesters gathered outside Woolwich Crown Court in south-east London for the first day of the U.S. extradition hearing on Monday, holding up banners reading "Free Assange". If found guilty, he could be sentenced to up to 175 years in prison.
"The principle of reciprocity is at the core of any extradition treaty", their spokesman Radd Seiger said.
Before his arrest there last April, he had been living since 2012 at the Ecuadorian Embassy in London to avoid extradition to Sweden after the surfacing of an alleged rape.
The family of Harry Dunn has urged the government to refuse the extradition of Julian Assange until the USA returns the suspect in his death back to the UK.
Fitzgerald said Assange was suffering as a result of the "declaration of war on leakers and journalists" by the administration of President Donald Trump.
Mr Seiger said Mr Dunn's family had been "badly let down" since his death and urged the government to "show us what they are made of, if they are to instil any confidence that they really do have our backs".
But Lewis, for the USA government, told the court, "Julian Assange is no journalist". But many others are critical of the way WikiLeaks has published classified documents without redacting details that could endanger individuals.
Defence barrister Edward Fitzgerald told the Woolwich Crown Court on Tuesday that the WikiLeaks founder has been handcuffed 11 times, stripped naked twice and put in five separate holding cells.
He asked the judge to consider Assange's treatment, as it was harming his "right to a fair trial".
But the Australian unexpectedly stood as the judge was about to rise for the lunch break, saying the sound of protesters outside the court was distracting. He complained that he was having difficulty concentrating and called the noise from outside "not helpful". "I understand and am very grateful of the public support and understand they must be disgusted".
Assange's extradition proceedings are to be divided into two parts: this first week of legal arguments, followed by two or three weeks of witness testimony in May.