The sentence that lifers have to serve in prison before they become eligible for parole came into sharp focus in a Constitutional Court ruling which was handed down on Friday.

This, after the court upheld a ruling of the Gauteng High Court in Pretoria which declared invalid a section of the Correctional Services Act.

Under the previous Correctional Services Act of 1959 (1959 Act), anyone sentenced to life imprisonment was eligible to apply for parole after serving a minimum of 20 years. In terms of the 1998 Act, however, someone serving a life sentence is eligible for parole only once they have served a minimum of 25 years, the Constitutional Court said in a media summary on Friday.

"Section 136(1) of the 1998 Act governs the transition from the parole eligibility requirements under the 1959 Act to those under the 1998 Act.  Section 136(1) provides that inmates sentenced before 1 October 2004 are subject to the 1959 Act and must serve a minimum of 20 years, but inmates sentenced after 1 October 2004 are subject to the 1998 Act and must therefore serve a minimum of 25 years," the summary continued.

Read: When does a prisoner qualify for parole?

Inmate Oupa Chipane Phaahla took the matter to court, challenging section 136(1) of the act on the basis that the use of the date of sentencing rather than the date when the crime was committed was a breach of his right to a fair trial under section 35(3)(n) of the Constitution.

The court declared the section invalid on the grounds that the impugned provision breached the constitutional rights to equal treatment by the law and not to be discriminated against unfairly.

Phaahla, was convicted on September 25, 2004.

On October 1, 2004, section 73(b)(i)(v) of the Correctional Services Act of 1959 changed and on October 5, 2005, Phaahla was sentenced.

Also read: South Africa's parole system to be revised

In a judgment penned by Acting Justice Daniel Dlodlo, the court confirmed the High Court’s declaration of invalidity.

"The majority held the impugned provisions invalid on the grounds that the use of date of sentence in section 136(1), rather than the date of commission of offence, breaches the constitutional right to equal protection of the law and also the right to the benefit of the least severe punishment.

"The majority held that it amounts to retroactive application of the law, which violates section 35(3)(n) and the principle of legality," the Constitutional Court explained.