Selebi, a former president of Interpol, was sentenced last year to 15 years in prison for taking bribes from crime syndicates in exchange for secret police information.

In a hearing before the Supreme Court of Appeal in Bloemfontein in central South Africa, his lawyer Jaap Cilliers on Tuesday challenged the credibility of the witnesses against Selebi.

“You should very seriously evaluate the opportunistic conduct of witnesses,” Cilliers told the judges, according to the Sapa news agency.

Selebi was convicted of accepting cash and lavish gifts bought on Harrods shopping sprees by a convicted drug dealer and others, amounting to more than 1.2 million rand (166,000 dollars, 129,000 euros) in bribes over five years.

The offences were committed between 2000 and 2005, during his time in office.

A judge described Selebi’s dealings as an “embarrassment” in South Africa’s highest-level corruption conviction ever.

State witness Glen Agliotti, a convicted drug dealer and accused in the murder of a local mining magnate, had testified about buying Selebi designer clothing, for which the police chief fed him inside information.

Cilliers said the case involved a group of witnesses who were “very opportunistic people”.

Selebi, who is out on bail, was not present in court due to ill-health, media reported.

His successor Bheki Cele was suspended by President Jacob Zuma last week after an investigation accused him of misconduct in approving leases for new police headquarters at inflated prices.