Hernán Giraldo Serna, one of the leaders of a rightwing force that escaped trial for crimes against humanity to face drug charges in the US, oversaw 270 murders

Hernán Giraldo Serna and the men who were under his command in a broad area of northern Colombia murdered more than 270 farmers, indigenous leaders and leftist organizers.

They forcibly disappeared and tortured many of their victims; thousands more fled their homes in fear. Giraldo won the nickname “the Drill” for the dozens of young girls and women he raped. Twenty-four bore his children.

But when Giraldo faces a federal court in Washington DC on Friday it won’t be for any of those crimes. Rather, he will be sentenced for conspiring to import cocaine into the United States when he was a leader of a rightwing paramilitary group through which he lorded over the northern slopes of Colombia’s Sierra Nevada de Santa Marta.

However, in a precedent-setting twist to the case, the family of Julio Henríquez, who was tortured and murdered by Giraldo’s henchmen in 2001, will be allowed to address the court about the impact of his crimes.

Friday’s hearing marks the first time that Colombia’s brutal paramilitary leaders – who escaped trial for crimes against humanity at home because of drug charges in the United States – will face their victims in a US court, according to the Henríquez family’s attorneys.

Roxanna Altholz, who represents the Henríquez family, said part of the conspiracy Giraldo has pleaded guilty to was offering armed protection to drug traffickers. “And part of that armed protection was Julio’s murder because he was undermining the drug trade by organizing farmers to replace coca for other crops,” she said. Coca is the main ingredient in cocaine.

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Nadiezdha Henríquez said that she, her sister Bela and their mother, Zulma, would tell the story of her father Julio’s murder one more time in the hopes of seeing some sort of justice. He was addressing a meeting with farmers when two masked men burst in, and dragged him into white pickup truck. He was never seen alive again.

“We want to make the court understand that there are people whose lives are destroyed by this supposedly victimless crime of drug trafficking,” she said in an interview in Bogotá before travelling to Washington. “We want to influence the judge’s decision on how long Hernán Giraldo will stay in prison.”

They will make a plea for the stiffest sentence possible, which is life in prison, and describe what it would mean for them and the communities of Colombia’s northern coast, where he once reigned, if he were to return home after a short sentence.

“He is a very dangerous figure for the people of that area. If he returns, he will resume his business and the fear we lived with for so many years will return,” said Zulma, Henríquez’s widow.

Giraldo, 68, is one of 14 former leaders of the United Self Defence Forces of Colombia (AUC) who were extradited to the United States on drug trafficking charges in 2008 just as they began to confess – as part of a demobilization deal – the human rights crimes they committed in their purported fight against leftist Farc rebels and anyone perceived to be a supporter.

Critics claimed that justice for thousands of murder, rape, torture and disappearance victims was thwarted by the paramilitary leaders’ extraditions, although most continued to cooperate with Colombian prosecutors investigating the crimes.

Giraldo is the last of those extradited to face sentencing, after he pleaded guilty to one count of conspiracy to traffic cocaine.

Prosecutors are asking for a 20-year sentence, which would be reduced by half through the 10 years he has already served since turning himself in 2006 in Colombia before his extradition the United States in 2008.

In a memorandum seen by the Guardian, Giraldo’s defence suggests a 12-year sentence, arguing that he was “compelled to become involved in the … AUC because of patriotism and a sense of duty, honor, and obligation to protect the peasant community” against leftist guerrillas.

The drug trafficking, according to Giraldo’s lawyers, was just a way to make money to maintain the counter-insurgency force.

In 2007, Henríquez’s body was found in a clandestine grave. He was missing his jaw and a foot. Two bullets had pierced his skull.

Two years later, after Giraldo had been extradited to the US, a Colombian court convicted him of Henríquez’s forced disappearance. He was sentenced in absentia to 37 years in prison and ordered to pay compensation to the family. But the sentence has not been executed because of the charges in the United States and a pending sentence under the special peace process mechanism.

But while Henríquez’s family has been unable to get redress in Colombia, they hope to find justice in the US court. And acceptance of Henríquez’s widow and daughters as victims in a case of international drug trafficking could open the door to future non-US victims of traffickers to have their say in court as well.

“Victims of [the Mexican drug boss Joaquín] Chapo Guzmán or other leaders of cartels or members of security forces or politicians who face drug charges could also face their victims in US court,” said Altholz.

“It’s a new way to look at drug conspiracies,” she said. “It says those tons of cocaine and ounces of heroin that reach the US are tainted with blood.”