Julian Assange, founder of WikiLeaks.

WikiLeaks creator Julian Assange was arrested in London on Thursday and faces extradition to the U.S. over a charge of conspiracy to commit computer intrusion under the Computer Fraud and Abuse Act. But lawyers not connected to the case said the single count brought by the U.S. District Court for the Eastern District of Virginia isn't a lock, and connecting communications and interactions will be crucial to proving conspiracy.

The charge, which was originally filed under seal March 6, 2018, alleges Assange and former U.S. Army intelligence analyst Chelsea Manning agreed to hack a password on a government computer. The cracked password, the government alleges, would have allowed Manning to log into government computers under a different username to access documents to share with Assange without the activity being traced to her.

As Assange is held in U.K. custody, prosecutors first hurdle may be securing his extradition from the United Kingdom.

Per the European Convention on Human Rights, extradition may be refused if Assange's offense is punishable with capital punishment, said Foley & Lardner partner and national security lawyer Christopher Swift. However, the maximum penalty for conspiracy to commit computer intrusion under the Computer Fraud and Abuse Act is five years, according to the Eastern District of Virginia press release announcing the charge.

If Assange finally lands on American soil, prosecutors will most likely use computer forensics and digital communications to connect Assange to conspiring to hack government computers.

“What I would expect is the government to have some communications that help them to paint the picture of the conspiracy that is alleged here and be pieced together with the actions that Manning took and show a timeline of actions, coordination and communication,” said Mayer Brown partner and former Executive Assistant U.S. Attorney for the Southern District of Florida Marcus Christian.

According to the indictment, ”Assange indicated [to Manning] that he had been trying to crack the password by stating that he had 'no luck so far.'” Such correspondence and Manning and Assange allegedly communicating through online chat services may indicate the DOJ has evidence of more conversations.

“They talk about specific communications between Assange and Manning and specific password cracking attempts,” said Christopher Ott, a Davis Wright Tremaine partner and former senior counterintelligence and cyber counsel with the U.S. Department of Justice's National Security Division. He added, “If it proves as direct as they describe, it could still be a hard case but it could be relatively straightforward.”

The actual publishing of stolen government files to Wikileaks will also help prosecutors to prove conspiracy, a lawyer said.

“Part of being able to build a conspiracy case is to establish that there is an underlying crime (or at least the planning and preparation for an underlying crime) because criminal charges like aiding and abetting and conspiracy are a form of secondary liability that can ride on the coattails of the underlying criminal offense,” said Fenwick & West of counsel and former federal prosecutor Hanley Chew.

On the defense's side, Assange's counsel will argue the facts and “poke holes in the sequence of events that the government must show to get a conviction,” Swift added.

Assange's lawyers have already said the arrest sets a dangerous precedent for journalists' rights, according to ABC News.

The American Civil Liberties Union and freedom of the press organizations issued statements condemning the charge against Assange. The ACLU said in part, “While there is no First Amendment right to crack a government password, this indictment characterizes as 'part of' a criminal conspiracy the routine and protected activities journalists often engage in as part of their daily jobs, such as encouraging a source to provide more information.”

In 2013, the U.S. Department of Justice decided not to pursue charges against Assange over publishing classified information because it would also have to prosecute other news organizations and journalists who've published classified material, according to a 2013 article in The Washington Post.

However, a First Amendment defense may be unsuccessful against the government's claim of a conspiracy to hack into unauthorized government files, said Fenwick & West of counsel Chew.

“He could definitely try that claim, but I'm not sure how successful it might be because I think as a journalist [there's a line] between getting a tip from someone and actively helping someone to commit a crime to get information.”