A top United Nations official is accusing U.S. authorities of imposing a penalty that amounts to torture against former Army intelligence analyst Chelsea Manning, who is currently jailed in a federal facility after refusing to testify to a grand jury investigating Wikileaks founder Julian Assange.

Earlier this year, a federal judge detained Manning and imposed on her daily fines after finding that she was in contempt of the court's order to testify.

Nils Melzer, the U.N. special rapporteur on torture, said in a letter he made public this week that detaining Manning and fining her with the aim of coercing her to testify constitutes a kind of torture that runs afoul of U.S. international human rights obligations.

Calling Manning's treatment a "deprivation of liberty," Melzer wrote that jailing and fining Manning fulfills "all the constitutive elements of torture, or other cruel, inhuman or degrading treatment or punishment. In my view, such measures do not fall under the 'lawful sanctions' exception" of the U.N.'s Convention Against Torture.

President Obama, in the waning days of his presidency, commuted Manning's original 35-year sentence for leaking classified government documents to Wikileaks to the 7 years she had already served.

But in May, U.S. District Judge Anthony Trenga sent her back behind bars to a federal detention facility in Alexandria, Va., for refusing a second time to offer testimony to a grand jury impaneled to investigate Assange.

Melzer noted in his letter to American authorities that Manning spent time in solitary confinement following her 2010 arrest. At the time the secret military files were exposed she went by the name Bradley Manning.

The terms of Manning's current detention are all the more alarming, Melzer wrote, given her previous ill treatment in prison.

"Victims of prolonged coercive confinement have demonstrated post-traumatic symptoms and other severe and persistent mental and physical health consequences," he wrote.

Manning was fined $500 the first 30 days of her confinement and then $1,000 a day for each day after that for refusing the testify. The accumulation of fees are set to continue for as long as the grand jury investigating Assange is convened, typically a period of 18 months.

Melzer, who sent the letter to American officials on Nov. 1 but made the document public only on Monday, is asking authorities in the U.S. to explain how Manning's punishment does not violate international human rights standards.

"Please provide information on how such coercive measures, which do not constitute circumscribed criminal sanctions, but which appear to intentionally inflict progressively severe suffering and financial pressure for the purpose of coercing individuals to testify against their conscience," he wrote.

In March, when Manning was first imprisoned for refusing to comply with the grand jury's request, her legal team called the punishment "pointless, punitive and cruel."

Added her lawyers: "Chelsea has clearly stated her moral objection to the secretive and oppressive grand jury process. We are Chelsea's friends and fellow organizers, and we know her as a person who is fully committed to her principles."

A spokeswoman for the Department of Justice did not return a request for comment.

Manning has become a national voice for gay and transgender rights and has continued to agitate for the disclosure of government secrets.

"These are our institutions. And what's their intent? To keep the public unaware of things — given the scale of the classification system — and to crush dissent," Manning said in 2017 during a book tour stop in Philadelphia. "This is not just about secrecy but about whether we have an open dialogue in our society."

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