The Office of the Special Prosecutor (OSP) has revealed that its behind-the-scenes investigative support to United States authorities contributed to the conviction of former Tema Oil Refinery (TOR) Managing Director, Asante Kwaku Berko in a high-profile international bribery case.

The OSP said on Monday, August 10, that it assisted the United States Federal Bureau of Investigation (FBI) with investigative and evidentiary material through Ghana’s established mutual legal assistance framework.

According to the anti-corruption agency, the support provided by Ghana was specifically recognised by the United States Department of Justice (DoJ) as having played a significant role in the prosecution.

“The involvement of the OSP has been acknowledged by the United States Department of Justice (DoJ) as providing ‘significant assistance to this prosecution'," the OSP said.

$1m bribery scheme

A federal jury in Brooklyn, New York, found Mr Berko guilty on August 6, 2026, of charges relating to a scheme to pay more than US$1 million in bribes to Ghanaian government officials between 2014 and 2015.

The case arose from efforts to secure the development and financing of a power plant in Ghana under an agreement between the Government of Ghana and Turkish energy company Aksa Enerji Uretim A.S.

Aksa was a client of Goldman Sachs, the US investment bank where Mr Berko previously worked.

The OSP said its cooperation with the FBI was conducted largely away from the public spotlight, with Ghanaian authorities providing evidence and investigative assistance to their US counterparts during the prosecution.

It said the outcome demonstrated the importance of international cooperation in tackling corruption cases that cross national borders.

Mutual legal assistance

The OSP further said the case illustrated the practical value of mutual legal assistance arrangements, which enable law enforcement and prosecutorial agencies in different jurisdictions to obtain and share information and evidence in complex investigations.

Mr Berko, who holds both Ghanaian and American citizenship, faces a maximum sentence of 30 years in prison following his conviction.

He has been remanded pending sentencing and is expected to return to the US court on November 10, 2026, for the sentencing hearing.

The conviction marks the latest development in a case that has drawn attention to the use of international law enforcement cooperation in pursuing alleged corruption involving public officials and cross-border commercial transactions.