The Constitutional Court has confirmed convicted killer Oscar Pistorius had served half of his sentence by 21 March this year.

This means he has been eligible for parole for more than six months.

After correctional services authorities dropped their opposition to Pistorius' bid to establish when exactly his 13-year-five-month sentence for the murder of his girlfriend, Reeva Steenkamp, came into effect, the apex court found the Supreme Court of Appeal (SCA) had correctly antedated that sentence to 6 July 2016. 

That was the date when Pistorius began serving his later overturned six-year sentence for murder committed under the principle of dolus eventualis.

For reasons that have yet to be explained, the SCA had recanted that order days before Pistorius was due to be considered for release on parole, in a letter whose legal status the apex court had sought to establish.

The Constitutional Court's ruling has now made it clear Pistorius should have been considered for release on parole in March.

Tania Koen, who represents Reeva Steenkamp's parents, said she agreed with the Constitutional Court's decision "as it was our view that Oscar Pistorius was eligible to be considered for placement in March 2023".

In response to the ruling, correctional services spokesperson Singabakho Nxumalo told News24: "The Department of Correctional Services [DCS] has received an order from the Constitutional Court on the proper interpretation of the Supreme Court of Appeal's judgment [on Pistorius' sentence] delivered on 24 November 2017.

"Briefly, the matter relates to the sentence given to inmate Oscar Leonard Pistorius, its effective date and the impact on the calculation of the minimum detention period.

"DCS is studying the order and shall in due course pronounce itself on the way forward. This shall ensure that the order of court is correctly executed."

Nxumalo said Pistorius' "minimum detention period" - which is the time he would need to serve before considered for parole - was half his sentence.