They were originally facing the lesser charge of manslaughter and could now be sentenced to death if convicted, the Information Affairs Authority said.
Post-mortem examinations last year found the victims had been shot at close range, a rights commission said.
A fourth policeman was also sentenced in absentia to five years in prison.
He was found guilty of assault after having wounded a protester by firing birdshot at them, the IAA said, adding that the officer himself was in hospital after suffering severe injuries in a bomb attack two months ago.
The trial of the officers accused of the murders of Ali Ahmed Abdullah, Issa Abdul Hassan and Hani Abdul Aziz Goma will resume on 10 July.
Compensation
In a related development, the Bahraini government said it would pay $2.6m to the families of some people killed during the uprising in February and March 2011.
"Disbursement of compensation to the families of 17 deceased persons has begun in keeping with the implementation of the recommendations of the Bahrain Independent Commission of Inquiry (BICI)," a statement said, citing a justice ministry official.
The government said the payments amounted to $153,000 per person.
The BICI reported in November that at least 35 people were killed between February and March 2011, 30 of them civilians and five security forces personnel. It also found that security forces had used excessive force and tortured detainees, including five who died.
Most of the demonstrators were from the Gulf kingdom’s Shia Muslim majority, which has long complained of discrimination at the hands of the Sunni royal family, the Al Khalifa, and wants democratic reforms.
Almost 3,000 people were also arrested by security services after King Hamad declared a state of emergency in March and asked fellow Sunni-led Gulf states to send in troops. Scores were tried by military courts and sentenced to prison terms of up to life after what human rights activists said were grossly unfair trials.
The king has tried to address some of the protesters’ demands by announcing constitutional reforms intended to lead to greater accountability. But opposition and human rights activists have complained that the violent crackdown on dissent is continuing.
