Four men convicted of murdering a lesbian near Cape Town have received 18-year prison sentences, days before the sixth anniversary of her death.

Openly gay Zoliswa Nkonyana, 19, was stabbed and stoned in the homophobic attack in Khayelitsha on 4 February 2006.

A total of nine men had been arrested, but Lubabalo Ntlabathi, Sicelo Mase, Luyanda Londzi and Mbulelo Damba were found guilty of the murder in October 2011.

The case was reportedly postponed more than 50 times. Sentencing was initially expected before Christmas.

The murdered woman’s stepfather Mr Mandini told South Africa’s Sowetan newspaper: “They did not accept responsibility for what they did and we are happy that when we asked for a lengthy jail term, the magistrate agreed to that.”

The Social Justice Coalition issued a statement last night on the conviction, highlighting what it called “consistent failures” of the police and justice system in the six-year case.

“Over the past six years, a number of Khayelitsha-based civil society organisations including the Social Justice Coalition, Treatment Action Campaign, Free Gender, Triangle Project and Sonke Gender Justice have attended Nkonyana’s court dates, monitored progress, spoken to prosecutors and tried to assist her family in finding justice.

“It is unlikely that this case would have concluded without the constant support and pressure from these organisations. We have held countless protests outside the Khayelitsha Magistrate’s Court and raised awareness in the media regarding this case.”

The Coalition concluded: “Today we remember Zoliswa and thousands of other people who have been needlessly murdered – many of whom have then had justice denied. We wish Nkonyana’s family well and hope they will be able to move forward from this trauma.

“However, we cannot forget the larger context. Unless changes are made and the police and criminal justice system improve, families will continue to suffer as the cases of their loved ones drag painfully through the system.”