Philippine human rights campaigner Leila de Lima was cleared of all criminal charges on Monday, ending years of legal battles for one of the most vocal critics of former president Rodrigo Duterte.

The former senator and justice minister had spent a decade investigating “death squad” killings allegedly orchestrated by Duterte until she was arrested in 2017 and spent more than six years in prison.

“I am now completely free and vindicated. It’s very liberating,” de Lima told reporters outside the courtroom in Manila.

De Lima, 64, had been freed on bail in November last year, having earlier been cleared of the two other drugs charges.

The last case concerned allegations she took money from inmates inside the country’s largest prison to allow them to sell drugs while she was justice minister from 2010-2015.

“The prosecution was not able to prove the guilt of all the accused beyond reasonable doubt,” regional trial court judge Gener Gito wrote in his verdict, acquitting de Lima and four other defendants of illegal drug trading.

De Lima was a sitting senator when she was arrested in 2017 and spent more than six years in jail while on trial for three drug trafficking charges.

She described the cases as payback for her efforts to investigate Duterte’s drug war, first as head of the government’s independent human rights body, then as justice minister and during her term as a senator.

She had maintained that the charges, which carried a maximum penalty of life in prison, were fabricated to silence her from criticising Duterte’s narcotics crackdown that left thousands dead.

Multiple witnesses, including prison gang bosses, died or recanted their testimonies during the lengthy trials.

Also dismissed on Monday was a second charge alleging de Lima had persuaded a former employee to ignore a 2016 summons issued by the House of Representatives for a hearing on the trade of illegal drugs in Philippine prisons.

The ruling said de Lima had been denied her “right to a speedy trial” as guaranteed in the Philippine constitution, having spent 2,321 days in jail while on trial in a case where the maximum penalty if convicted is 180 days in prison.

That case was the only other remaining criminal proceeding against her, her lawyers said.

Before her arrest, de Lima spent a decade investigating Duterte’s drug war during his time as mayor of the southern city of Davao and early in his 2016-2022 presidency.

Thousands of drug suspects were killed by police and unknown gunmen in a campaign that became the centrepiece of Duterte’s 2016-2022 rule, a crackdown that critics described as state-sponsored extrajudicial killings and is now a subject of an investigation by the International Criminal Court.

De Lima said on Monday that she will continue to help the tribunal in its investigation.