Former Gambian interior minister Ousman Sonko goes on trial in Switzerland on Monday accused of crimes against humanity committed under the regime of ex-dictator Yahya Jammeh.

The trial takes place under the principle of universal jurisdiction, which allows a foreign country to prosecute crimes against humanity, war crimes and genocide regardless of where they were committed. 

Sonko was interior minister in The Gambia — a small West African nation ruled with an iron grip by Jammeh from 1994 to 2016.

He has been in custody since his arrest in Switzerland in January 2017 after applying for asylum following his sacking as a minister.

Sonko, who turns 55 years old on Tuesday, was detained after a complaint by Geneva-based NGO Trial International.

He is "the highest-ranking state official ever to be tried for international crimes in application of the principle of universal jurisdiction in Europe", Leslie Haskell, president of Trial International, said in a statement.

Sonko is accused of "having supported, participated in and failed to prevent systematic and generalized attacks as part of the repression carried out by the Gambian security forces against all opponents of the regime".

He denies all the charges, according to his lawyer Philippe Currat. 

If found guilty, he faces life imprisonment.

'Hope for answers'

The trial, which is due to last a month, takes place in the town of Bellinzona in Switzerland's southern Italian-speaking region.

But proceedings will be held in German, one of Switzerland's four national languages, leading to complaints by lawyers who are unhappy that only parts of the hearing will be translated into English, making it more difficult for Gambians to follow.

A verdict is not expected before March.

The charges span a 16-year period and include nine counts of crimes against humanity including murder, rape and torture.

There are 10 complainants in the case, who include eight "direct victims" and the daughter of a person who died in detention, according to Trial International.

"This trial offers hope for the victims of several decades of repression in The Gambia to get answers about the crimes committed against the Gambian population," Trial's legal adviser Benoit Meystre told AFP.

It is Switzerland's second crimes against humanity trial.

In June, a Swiss appeals court upheld a 20-year sentence for former Liberian warlord Alieu Kosiah, confirming his war crimes conviction and, for the first time in Swiss history, handing down a verdict of crimes against humanity.

Iron grip

Jammeh ruled The Gambia for 22 years but fled the country in January 2017 after losing a presidential election to relative unknown Adama Barrow. 

Jammeh refused to acknowledge the results but was forced out by a popular uprising and fled to Equatorial Guinea.

Before becoming a minister, Sonko was inspector general of The Gambia's national police and also served as commander of the national guard, responsible for the president's protection.

Currat, Sonko's lawyer, says responsibility for events described on the charge sheet falls to the national intelligence agency and not his client.

"This agency has never been under the authority or control, in fact or law, of Ousman Sonko," Currat told AFP.

Caroline Renold, a lawyer for three of the complainants, said that Sonko could not have failed to know about "all the atrocities which were committed while he was a senior official in the security system".

"And on the other hand, he is accused of having participated directly in atrocities," she told AFP.

The trial is not the first dealing with Jammeh-era crimes to be held outside of The Gambia.

In late November, a German court sentenced a Gambian man to life in prison over his participation in a death squad that assassinated opponents of Jammeh.

Gambia's government said last year it was working with West African regional bloc ECOWAS to set up a tribunal to try crimes committed under Jammeh.