The police mugshot of Senator Leila de Lima may be a little grainy, but her expression is clear. It says: I am not afraid.

It’s a stoicism the former secretary of justice of the Philippines has kept up since she was arrested last month on drug-related charges many believe are a thinly veiled attempt to silence the outspoken critic of President Rodrigo Duterte’s war on drugs. That war has claimed the lives of more than 7,000 people since Duterte took office in June, many of them in extrajudicial killings that have horrified human rights campaigners who say he is steamrolling the rule of law.

Against such a background, De Lima has plenty of reasons to fear for her safety – not least among them the fact she now resides in a 120 sq ft cell at the national police headquarters alongside 25 male detainees – some of whom she herself investigated and indicted.

Yet De Lima is a fighter, and isn’t afraid of bringing her fight to the world. When a press scrum surrounded the police van taking her into custody on February 24, she wore that same calm expression she would later use for the mugshot, staring into the cameras and signing an “L” for laban (fight).

“My arrest is an appalling sign of the return of a power-hungry, morally bankrupt and abusive government. As we expected, the Department of Justice filed criminal cases against me based on manufactured stories accusing me of involvement in the drug trade,” the senator said before her arrest.

“I have long prepared myself to be a political prisoner of this regime.”

More than a week on and De Lima’s defiance is burning no less brightly.

“She is in high spirits and confident as usual as she believes her conscience is clear,” said Karen Gomez-Dumpit, commissioner of the Commission on Human Rights (CHR), who has visited De Lima since her arrest.

Like most people close to the senator, Gomez-Dumpit described De Lima, 57, who preceded her at the commission, as someone of the highest integrity who was incorruptible, willing to meet anyone and whose resolve would not be easily broken.

Such qualities had made De Lima a perfect fit for the commission when she was posted there in 2008 by then president Gloria Macapagal Arroyo.

Gomez-Dumpit recalled a workshop she attended with De Lima in a hotel. Afterwards, when the hotel gave De Lima a towel as a gift, she declined.

“Her policy was that she did not take any gifts. I think that if you are good in the little things, then surely you will be honest with the big things,” Gomez-Dumpit said. “She lives a simple lifestyle. Just at look her glasses, watches and jewellery. She never wears girly things.”

De Lima won plaudits for her work at the commission investigating human rights violations, but it was also here that her current fate may have been sealed – when she initiated a probe into Duterte’s alleged links to the Davao Death Squad, an anti-drugs vigilante group responsible for more than 1,000 deaths during Duterte’s stint as Davao mayor.

De Lima left the probe unfinished when she became secretary of justice in 2010 – a post she would remain in for a further five years before being elected as a senator last year. Her supporters, however, believe the issue festered, finally coming back to haunt her following Duterte’s election as president in June.

The qualities that had made De Lima such a good fit at the CHR are in stark contrast to the charges against her. She is accused of letting a convicted felon run a drug business from inside prisons and of receiving 5 million pesos (HK$770,000) in bribery money during her time as secretary of justice.

Those charges were brought by the Justice Department, headed by Secretary of Justice Vitaliano Aguirre II, a fraternity brother of Duterte’s.

For his part, Duterte has made little secret of his animosity towards De Lima. “I will have to destroy her in public,” he said while raising allegations about her involvement with drug lords. He has also suggested the senator “hang herself”.

The feeling is mutual; De Lima has described Duterte as a “sociopathic serial killer”.

Jacqueline de Guia, the CHR spokeswoman and attorney, who worked with De Lima for two years, said she could not believe the accusations against her.

“Her integrity cannot be doubted. She never demonstrated a tendency to corruption,” De Guia said.

Attorney Diana de Leon, the CHR’s chief investigator, said her personal view was that De Lima was “one of the most efficient and competent” leaders the commission had ever seen.

“She feared no one and would not hesitate to recommend the filing of cases against high ranking and very influential officials of the government.”

Of course, if De Lima’s supporters are to be believed, it is just such a quality that has led to her featuring in police mugshots and pacing around a tiny cell.

The drug-related cases De Lima faces were based on the testimony of convicted felons and former prison officials during a congressional inquiry on drug trade in national prisons.

Walden Bello, a former member of the Philippines Congress, said De Lima was being made an example of how anyone who opposed Duterte could be destroyed politically. “For politicians and government bureaucrats – both those with links to drugs and no links to drugs – this naturally raises the nagging question, ‘Am I on that list?’ It’s a very effective way to silence potential critics,” he said. “I think the president may have committed a grave error in having De Lima incarcerated on very flimsy charges obtained from drug offenders who have an interest in giving the so-called evidence demanded by the administration.”

Whether that evidence is enough to keep De Lima behind bars is unclear. While her lawyers have filed a petition for her release, the offences are non-bailable under the country’s anti-drug laws and a guilty verdict if and when her trial takes place – a process that could take years – would bring a penalty of life imprisonment.

What is clear is that De Lima won’t be cowed into submission. Before her arrest, she had a message for the world: “I urge people with conscience everywhere, please pray for the Philippines,” she said. “I ask you to remain vigilant and continue to fight, so that true justice and respect for human rights prevail.”

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