A South African appeal court has more than doubled the former Paralympian Oscar Pistorius’s prison sentence for murdering his girlfriend, Reeva Steenkamp.

The supreme court of appeal (SCA) increased Pistorius’s sentence from six years in prison to 13 years and five months.

Pistorius killed Steenkamp by firing four bullets from a handgun through a closed toilet door in his luxury home in Pretoria on Valentine’s Day 2013. He claimed he mistook her for a burglar.

Steenkamp’s family welcomed the increased sentence and said it showed that justice could prevail in South Africa.

“This is an emotional thing for them. They just feel that their trust in the justice system has been confirmed this morning,” Tania Koen, a spokeswoman for the Steenkamp family, said.

High court judge Thokozile Masipa initially sentenced Pistorius to five years for culpable homicide in 2014. The sentence was much lower than many had expected and was widely criticised.

He served only 10 months of the five-year sentence in prison before being released and put under house arrest.

The state appealed against the culpable homicide conviction, and it was later replaced with murder by the SCA in 2016. Masipa handed down a six-year jail term in July 2016 – described as “shockingly lenient” by state prosecutors.

The athlete was not in court for Friday’s ruling, where the court handed down the minimum 15-year sentence prescribed for murder in South Africa, then subtracted the years Pistorius had already served in jail.

Critics said Pistorius had received preferential treatment as a wealthy, white celebrity.

Pistorius, who turned 31 on Wednesday, has always maintained he fired in the mistaken belief that an intruder was hiding behind the door.

His lawyers have just one avenue open to them if they want to challenge the new sentence handed down by the Supreme Court, and that is to appeal to the constitutional court, the highest court in South Africa.

The Guardian