The Austrian Justice Ministry confirmed today that the Karners would be handed over to the US authorities, while the US Embassy in Ljubljana told the STA the extradition would take place this Friday.
The couple's lawyer, Roland Grilc, labelled the decisions as a "surprise", according to today's report by the daily Večer.
He said in Austria, the couple faced a maximum sentence of three years in prison, while in the US, they could serve as many as 40 years. "Austria apparently caved in to the pressure," Grilc told Večer.
The extradition request from the US is based on an indictment and an arrest warrant for the couple issued in Massachusetts on 3 March 2010.
The US authorities suspect the Karners of selling several hundred thousand vials of anabolic steroids between 2000 and 2008.
The couple was apprehended by the Austrian police on 27 December in an operation conducted in cooperation with US and Italian law enforcement.
The 33-year-old Alenka Karner and 36-year-old Mihael Karner are suspected of managing a network of steroid dealers who had sold around EUR 38m worth of the illegal substance over the internet. The police say the couple subsequently laundered the money through real estate investments.