A German engineer has gone on trial in Germany charged with aiding Libya's defunct nuclear weapons programme.
Mr Lerch is suspected of helping to develop a gas centrifuge
Gotthard Lerch, 63, is charged with breaking arms and exports laws for his role in providing technology for a gas centrifuge for Libya.
Mr Lerch, who was allegedly paid $34m (£19m), denies the charges.
He is the first alleged member of the arms smuggling network involving Pakistani scientist, Abdul Qadeer Khan, to face trial.
Prosecutors say Mr Lerch's contacts with the scientist, known as the father of Pakistan's nuclear programme, enabled him to set up and also co-ordinate supplies to Libya.
A gas centrifuge can be used for enriching uranium for use either as fuel in a civilian power programme, or to make nuclear weapons.
As the trial opened in Mannheim, Mr Lerch's lawyers filed a motion calling for three of the six-judge panel to be removed from the case for alleged bias.
They claim the judges denied Mr Lerch's team full access to the prosecution's evidence, the Associated Press news agency reported.
Earlier, his lawyer said the court would need to get information from foreign intelligence services, such as the CIA, in order to establish what really happened.
The BBC's Tristana Moore in Germany said the case was expected to shed light on the scale of international nuclear smuggling networks.
The case dates back to 2003, when centrifuge parts were seized on board a German-registered ship heading for Libya.
It prompted the Libyan regime to declare its nuclear plans and agree to abandon them.
Mr Lerch has been in a German prison since last summer after being extradited from Switzerland, where he was arrested in 2004.