Police say they are powerless to arrest an Algerian couple who fled the country while under suspicion for killing their baby son, writes Susan Greenwood.

Idriss Lallali, 32, an employee of the oil company BP and his wife Nassera, 29, disappeared while on police bail in June 2004 following the suspicious death of their nine-month old son Aymen.

At an inquest at Southwark Coroner's Court on January 31, a verdict of unlawful killing was recorded.

It heard that emergency services received a 999 call in June 2004 from the couple at their address in Blenheim Gardens, Kingston asking for help. Aymen was pronounced dead on arrival at Kingston Hospital and police were alerted by the ambulance service who suspected the controversial shaken baby syndrome (SBS).

The couple, who are believed to have returned to their homeland, moved to Kingston from Aberdeen shortly after Aymen's birth when Mr Lallali took up a job at BP's offices in Sunbury.

Despite having a warrant for the couple's arrest, police are unable to conduct inquiries in Algeria or enforce extradition orders with the African country because no reciprocal legal treaty exists with the UK.

Detective chief inspector David Shepherd said: "We have a warrant for the parents' arrest.

"They were on police bail and they then fled the country to Algeria but we don't have any extradition orders to bring them back.

Mr Lallali worked for oil giants BP both in Scotland and Sunbury and people who knew the couple spoke of their shock over the event saying both parents doted on their only child.

But the authorities remain convinced that there is a case against the Lallalis to be answered.