Jestina Mukoko said the charges had not made sense
Terrorism charges against a prominent Zimbabwean rights activist have been thrown out after a court ruled she had been tortured while in custody.
The Supreme Court granted Jestina Mukoko a permanent stay of prosecution after she told how security agents took her from her home and beat her.
She was accused of plotting to topple President Robert Mugabe.
Critics say the charges were fabricated in an attempt to silence opponents of Mr Mugabe's Zanu-PF party.
Analysts say the dropping of the charges could ease tensions in Zimbabwe's power-sharing government.
Chief Justice Godfrey Chidyausiku dismissed the case against Ms Mukoko and nine other defendants.
Lawyers for Ms Mukoko told the court that she had been subjected to simulated drowning, locked in a freezer and beaten as the security forces tried to make her confess to plotting to overthrow Mr Mugabe.
The chief justice accepted their claims.
"The state, through its agents, violated the applicant's constitutional rights... entitling the applicant a permanent stay of criminal prosecution," Mr Chidyausiku said.
At least three others are still facing trial on the same charges.
Ms Mukoko wept and hugged friends as she heard the judgment, saying the charges had not made sense.
"Justice has just prevailed. I'm so excited at becoming a free person again in Zimbabwe," she told journalists outside the court.
"For a while I have been someone who was not free, but with this freedom, I need to enjoy [myself]."
She said she was "passionate" about being a human rights activist and would continue in her profession.
Ms Mukoko, who had been free on bail since May, disappeared from her home in early December 2008 and was not heard from for three weeks.
The government denied holding her, but at the end of the month she appeared in court facing terrorism charges.
At the end of 2008 dozens of activists claimed they had been abducted by the security services.
Some of them were freed after short spells in detention and others were charged.
Many of the detained were supporters of Prime Minister Morgan Tsvangirai's Movement for Democratic Change (MDC).
Their detention caused huge tension between Zanu-PF and the MDC, who signed a power-sharing agreement last year.
Mr Tsvangirai spoke out on the issue earlier in the year, saying Ms Mukoko's case undermined the power-sharing deal.
An MDC spokesman says the activists should now be compensated for the harm they suffered while in custody.
Political analyst and Mugabe critic John Makumbe said it was a "positive thing" that the activists had been freed.
But he added: "I hope the state will comply with the ruling because in the past they [the state] have rearrested people on fresh trumped-up charges."
Donors are reluctant to resume aid flows to Zimbabwe because of allegations of continued human rights abuses in the country.