Bashir faces 10 charges, including three of genocide as well as war crimes and crimes against humanity in the western Darfur region.
The Hague: South Africa will on Friday seek to defend its failure to arrest visiting Sudanese President Omar al-Bashir who is wanted on charges of genocide, at an unprecedented hearing before international war crimes judges.
It will be a humbling moment for Pretoria, one of the leading voices in the creation of the International Criminal Court, whose lawyers will be fending off accusations that it failed in its obligations to the tribunal.
To the frustration of the ICC's prosecutors, Bashir remains in office and at large despite two international warrants for his arrest issued in 2009 and in 2010.
He faces 10 charges, including three of genocide as well as war crimes and crimes against humanity in the western Darfur region.
The deadly conflict broke out in 2003 when ethnic minority groups took up arms against Bashir's Arab-dominated government, which launched a brutal counter-insurgency.
At least 300,000 people have since been killed and 2.5 million displaced in Darfur, the UN says. Several victims of the lingering conflict in the western Sudanese region, who now live in The Netherlands, will attend Friday's hearing which opens at 0730 GMT in the tribunal in The Hague.
Long wait for justice
The UN Security Council asked the ICC as long ago as 2005 to probe the crimes in Darfur where conditions remain "dire," according to Monica Feltz, executive director of the rights group, International Justice Project.
The 10 Darfurians who will watch the hearing are "hoping to see that their story is told, and that their voices are heard, and that the international community still cares," Feltz told AFP.
"They're been waiting for over eight years to see justice in this case," she added, voicing disappointment the victims were not granted permission to actually take part in the hearing.
The issue is centred on South Africa's refusal to arrest Bashir when he attended an African Union summit in Johannesburg in June 2015, insisting he had "head of state immunity" and allowing him instead to slip out of the country.
The judges will have to decide whether Pretoria violated its obligations under the court's founding Rome Statute by not arresting him and handing him over for trial.
South Africa insists it was caught on the horns of a dilemma: between its obligations to both the ICC and to laws providing heads of state with immunity.
'No-one is above the law'
The ICC's prosecutors have hit back, pointing out that in the past South Africa told Bashir he would be arrested if he set foot in the country.
"No one is above the law, even heads of state," insisted Feltz.
Friday's hearing is "a historic opportunity for the court to demonstrate that its charges must be taken with extraordinary seriousness," said Wanda Akin and Raymond Brown, two legal representatives of the victims, in a joint statement.
They urged the court to send "an unmistakable message that open defiance of its writ will not be permitted."
The judges will return their decision at a later date, and may decide to report South Africa to the UN Security Council for eventual sanctions.
Although this is the first public hearing of its type, last year the ICC referred Chad, Djibouti and Uganda to the UN for also failing to arrest Bashir. So far no action has been taken against them.
The Sudanese leader was a guest last month at an Arab League summit hosted by Jordan -- also a signatory to the Rome Statute.
South Africa moved this year to withdraw from the court, angered by the case against it. But it formally revoked its decision last month after its own High Court ruled in February that it would be unconstitutional.
Although the date of the hearing was set late last year, it also comes at a moment of political tension in South Africa as embattled President Jacob Zuma faces growing calls to resign.