Lebanon's military court has acquitted Amer Fakhoury, 57, who was accused of overseeing the torture and murder of thousands of people while working as a prison guard in southern Lebanon more than a decade ago.
State Prosecutor Ghassan Oueidat has called on the state commissioner to the Military Tribunal to appeal against the decision.
Fakhoury was a former member of the now-disbanded South Lebanon Army (SLA) – a proxy militia backed by Israel during the 1982–2000 occupation of Lebanon.
Nicknamed the "Butcher of Khiam", after he served as a prison guard in Khiam prison in the 1980s and 1990s, Fakhoury allegedly personally oversaw the murder of several inmates.
At least ten people are believed to have died at the Khiam prison during Fakhoury's tenure.
The charges were dropped because the statute of limitations had expired, state-run National News Agency (NNA) reported yesterday.
The court ordered the immediate release of Fakhoury, unless he faces further charges.
A case filed by former Khiam prisoners who alleged torture by Fakhoury is still being followed up by a Beirut investigative judge.
No arrest warrant has been issued for these charges, essentially making Fakhoury a free man.
In response to the acquittal, detainees in the notorious Roumieh prison in central Lebanon started a riot to protest the "unfair release of Fakhoury".
Aya Majzoub, Lebanon researcher for Human Rights Watch, said the move "makes a mockery out of Lebanon's justice system".
While a statement released by Hezbollah said, "this day is sad for Lebanon and justice… the military tribunal, unexpectedly, has taken this wrong decision", and blamed "US pressures" for the acquittal.
The US had threatened renewed sanctions against the Iranian-backed Shia militia to press for the release of Fakhoury.
While Senators Jeanne Shaheen and Ted Cruz introduced legislation in February which would impose sanctions, including revocation of visas, on Lebanese officials deemed to be involved in the unlawful detention, arrest or abuse of a US citizen.
Fakhoury has been jailed since 12 September after his passport was seized upon entry to the country, which he was visiting to see family after two decades.
The former prison guard has since been diagnosed with stage four cancer and has not attended questioning sessions in the past few months due to hospitalisation.