An autopsy into the cause of death of a Nigerian asylum-seeker, who died during deportation, has concluded that he suffocated to death and that the police officers involved did not use excessive force.
The results of the autopsy, released on Thursday, concluded that Samson Chukwu's death was the result of a "fatal chain of circumstances", and that it could not have been foreseen.
The investigating magistrate, Jacques de Lavallaz, said the factors contributing to Chukwu's death were the method by which he was subdued - a police officer brought his weight to bear on the deportee's back - as well as his recent physical efforts, and stress.
"It was a fatal chain of circumstances," said Lavallaz. "To my knowledge, the technique used to immobilise the prisoner is used by all police forces."
He added that further investigations into the police officer's handling of the incident were pending, as were related investigations to determine whether police recruits should be taught additional precautions to deal with people resisting arrest.
Chukwu, 27, man died in May while being restrained during attempts to transport him from a detention centre in canton Valais to Zurich airport. Police said he had become violent and that they were obliged to subdue him by handcuffing his hands behind his back, while he was face down on the floor.
The original report into his death said that during the procedure the officers noticed he had lost consciousness and stopped breathing. After attempting to resuscitate him, they summoned emergency medical assistance, but their efforts to revive him were unsuccessful.
The Nigerian had been in custody awaiting deportation for several months after being detained for drugs' offences. The Cantonal Foreigners' Service had said he had been disruptive during his detention, but he had shown no signs of illness.
A similar case occurred in March 1999, when a Palestinian deportee, Khaled Abuzarifa, suffocated after being bound and gagged during his deportation.
A court in canton Zurich this month handed down a five month suspended sentence to a doctor involved in the case, who was charged with death through negligence. The court concluded that the doctor had misdiagnosed the detainee's breathing problems, which he dismissed as a pretence.
The judge also said the doctor had failed in his professional obligations by allowing the deportee to be gagged but refusing to accompany the police officers and the prisoner to the airport.
In addition to the five month suspended prison sentence, the doctor was ordered to pay SFr50,000 ($28,000) in damages to Abuzarifa's family.
The two policemen involved in the case were acquitted.
As a result of that death, the use of tape to cover the mouth or any interference with the airways has been banned.
swissinfo with agencies