The Supreme Court will hear an appeal by imprisoned former MP Geoffrey Mwilima on Thursday.

The 68-year-old Mwilima has been in jail since August 1999, following his arrest in the wake of secessionist attacks that took place at Katima Mulilo in the then-Caprivi Region.

Late last year, the former lawmaker failed in his bid to get a High Court order for his release from prison.

Mwilima wants to be released on medical grounds, disclosing that he suffers from diabetes and kidney ailments.

However, Judge Marlene Tommasi dismissed Mwilima's application, saying that although the medical officer at the Windhoek Correctional Facility acknowledged that the latter suffers from life-threatening medical conditions, he does not qualify for medical parole.

The Correctional Service Act states that the minister responsible for Namibia's prison system may, on the recommendation of a medical officer, authorise the release of a prisoner suffering from a dangerous, infectious, or contagious disease or a prisoner whose continued incarceration is deemed detrimental to his or her health.

Tommasi found that the grounds on which Mwilima applied for that order "are premised on an erroneous and absurd interpretation" of a section of the Correctional Service Act.

She said the intention of that section of the law is to provide for the release of a prisoner suffering from a dangerous infectious disease or a dangerous contagious disease, and not for the release on medical grounds of an inmate with a life-threatening disease that can still be treated while the person is incarcerated.

The medical officer at the facility found that continued incarceration of Mwilima would not be detrimental to his health.

Though arrested in 1999, Mwilima was only sentenced in 2015 to an effective 18-year jail term, which was later reduced to 15 years.