Switzerland’s supreme court upheld a 20-year jail sentence for former Liberian rebel commander Alieu Kosiah on Friday, but overturned a conviction for crimes against humanity.

In 2021, Switzerland’s Federal Criminal Court found Kosiah, now 51, guilty of multiple atrocities committed during the first of Liberia’s back-to-back civil wars, in which about 250,000 people died between 1989 and 2003.

In 2023, the court’s appeals chamber upheld his 20-year sentence for war crimes and, for the first time in Swiss history, also made a new ruling that Kosiah was guilty of crimes against humanity.

The Federal Supreme Court of Switzerland was asked to review the case, and its verdict, dated September 28, was published on Friday.

The court “rejected the appeal filed by a high-ranking Liberian military official challenging his conviction for violations of the laws of war committed between 1993 and 1995 during the first Liberian civil war”, it said in a statement.

“However, the court has acquitted the individual of the charge of crimes against humanity, based on a strict application of the principle of non-retroactivity.”Switzerland recognises the principle of universal jurisdiction, which allows it to prosecute individuals suspected of international crimes, regardless of where those crimes were committed.

The court said the offence of crimes against humanity – introduced into Swiss law in 2011 – could not be applied to acts committed before then.

Kosiah’s conviction for violating the law of war was upheld, as was the maximum 20-year custodial sentence imposed.

“The decision makes final the first war crimes conviction ever handed down by a Swiss civilian court, and the first conviction anywhere of a Liberian for war crimes committed during the country’s civil wars,” said the Swiss organisation Civitas Maxima, which works to bring perpetrators of international crimes to justice.

A security guard peers through the door of the Doctors Without Borders compound near the US embassy in Monrovia, Liberia, on July 23, 2003 [File: Ben Curtis/AP Photo] Kosiah settled in Switzerland in the late 1990s and was arrested in 2014.

“Today the survivors of Alieu Kosiah’s crimes have final justice,” said Civitas Maxima director Alain Werner, who represents victims in the case.

“We are, however, deeply disappointed by the acquittal on crimes against humanity. What happened in Lofa between 1993 and 1995 is the very definition of a crime against humanity.”Like war crimes, crimes against humanity refer to atrocities, including murder, torture and rape. However, instead of isolated or sporadic events, the charge is used for incidents carried out in a widespread or systematic way.

In the 2021 verdict, Kosiah was found guilty of a slew of war crimes committed as commander of the United Liberation Movement of Liberia for Democracy rebel group.

He ordered or participated in the killing of 17 civilians and two unarmed soldiers, as well as rape and the deployment of a child soldier, the court ruled.

He had also ordered looting and repeatedly ordered, or had himself inflicted, cruel and humiliating treatment of civilians and mishandled corpses, according to the verdict.