In 2017, WikiLeaks released more than 8,000 pages of secret materials -- which the antisecrecy organization called "Vault 7" -- detailing the CIA's cyberespionage arsenal, including the agency's playbook for hacking smartphones, computer operating systems, messaging applications and internet-connected televisions.

It was one of the largest breaches in the agency's history. Federal prosecutors say the defendant, Joshua Schulte, stole the documents when he worked in a CIA unit that designed the hacking tools.

Schulte, 31 years old, faces 11 criminal counts, including illegal gathering and transmission of national defence information -- charges that derive from the Espionage Act, a statute that has been applied in other WikiLeaks cases.

Some of the charges relate to Schulte's alleged misconduct and obstruction following his 2017 arrest -- prosecutors say he lied to law enforcement and disobeyed court orders.

Schulte and his lawyers have called the espionage charges vague and overreaching, saying they infringed on constitutional free speech rights. They have alleged fatal errors in the government's case, objected to the secrecy shrouding the investigation and protested Schulte's isolated confinement in a Manhattan jail. Opening arguments in the trial are expected as soon as Tuesday, once jury selection is completed.

Schulte is one of the least appealing Wikileakers.  He was originally held on child porn charges and once called for fellow leaker Chelsea Manning to face the death penalty for spying.