Two police officers were indicted for the 2007 assassination of former prime minister Benazir Bhutto and will face trial along with five members of the Pakistani Taliban, a state prosecutor said.
The policemen were charged with failing to provide Ms Bhutto with proper security and with destroying evidence, said the prosecutor, Zulfikar Ali.
Their indictment triggers a new trial for the Taliban members so that all seven defendants can be tried together, he said.
Ms Bhutto and 23 other people were killed on December 27, 2007, in a gun and suicide bomb attack as she was leaving a rally in the garrison town of Rawalpindi.
She was campaigning there to return her Pakistan People's Party to power in parliamentary elections just weeks after returning to the country from years in self-imposed exile.
A UN commission said the assassination could have been prevented and blamed all levels of government for failing to provide adequate security.
It also accused intelligence agencies and other officials of severely hampering the investigation into those behind her murder.
The two police officers are accused of ordering the crime scene to be hosed down within minutes in what investigators believe was a deliberate attempt to destroy evidence, the prosecutor said.
A judge read out the charges against all seven defendants during a closed-door hearing at a prison in Rawalpindi, he said.
The UN commission's report said the Rawalpindi police's decision to hose down the crime scene and its failure to collect and preserve evidence "inflicted irreparable damage to the investigation".
The government of then military ruler Pervez Musharraf blamed Ms Bhutto's death on Baitullah Mehsud, a Pakistani militant commander with reported links to al-Qaida who has since been killed.
But Ms Bhutto's party has repeatedly hinted that Mr Musharraf or his allies were involved.
Ms Bhutto's Pakistan People's Party won the most seats in elections in February 2008 weeks after her killing. Asif Ali Zardari, Ms Bhutto's husband, won the presidency months later after forcing Mr Musharraf to quit the post.