Abdul-Sattar al-Birqdar, the spokesman of the Supreme Judicial Council, said Hashimi is being tried in absentia, China's state-run Xinhua news agency reported.
The case opened with plaintiffs and witnesses testifying about alleged assassinations of a director general in the national security ministry, an officer in the interior ministry and a lawyer, Birqdar said.
The trial of Hashimi and his guards has been delayed twice in the past two weeks after Hashimi's attorneys told an appeals court his trial should not be in criminal court but in the Federal Court. The request has been rejected twice.
Hashimi faces more than 150 charges. His 73 guards face more than 300 charges.
"There are many crimes that Hashimi and his bodyguards are accused of and we have confessions from them, including the assassination of six judges," Birqdar said.
An arrest warrant was issued against Hashimi in December 2011 on charges of running death squads.
Interpol has issued a Red Notice against him for alleged terrorist acts. The Red Notice is an international alert to Interpol member states for help locating and arresting the vice president on terrorism charges brought by Iraqi Prime Minister Nouri al-Maliki.
Hashimi has denied the charges against him and said they are politically motivated.