There were angry scenes outside a South African court where eight suspects appeared for the first time in connection with an alleged gang rape.
The case has caused outrage after a video showing the suspects laughing during the alleged rape of a 17-year-old girl went viral.
Prosecutors want a psychiatric evaluation of the victim who is said to have the mental age of a five year old.
The case has been postponed until 25 April to allow further investigations.
The preliminary hearing was held behind closed doors because some of the suspects, who have been charged with rape and kidnap, are under-age.
A spokesman for the National Prosecuting Authority told South Africa's eNews television that if the girl is found to be mentally unstable, it would be classified as a serious offence punishable by possible life imprisonment.
The suspects will also be facing charges of creating and possessing child pornography - after a video taken of the alleged gang rape was widely circulated on mobile phones and the internet.
'You are forcing me'
A group of women demonstrated outside the Johannesburg courtroom when the eight people - including minors - arrived under heavy guard.
Dressed in the yellow, black and green colours of the ruling African National Congress Party, they sang anti-apartheid struggle song - holding posters that read "let them rot in jail" and "done with rapists", the South African Press Association reported.
"If you are a man you must use your brain to think, not your trouser[s]," Eyewitness news quotes Faith Mazibuko, Gauteng's community safety minister, telling the small crowd.
The video allegedly shows the suspects - the youngest of whom is 14 - laughing and joking during the alleged rape in the township of Soweto.
The girl went missing in March and her whereabouts were unknown until reporters from South Africa's Daily Sun newspaper brought the video to the attention of the police.
The paper reports that the video lasts just more than 10 minutes and the girl can be heard shouting: "You are forcing me, you are forcing me".
The video went viral on Wednesday, and was one of the main topics trending on social networking site Twitter.
The girl was found by police on Wednesday - and seven rape suspects were arrested in Soweto on Tuesday after they were matched to the video recording, the South African Press Association reports.
The man in whose home the girl was found has also been arrested and charged with kidnap.
Authorities have warned anyone who has received a copy of the video that they should delete it or risk being charged under the country's sexual offences laws.
Lulu Xingwana, South Africa's minister for women and children, issued a statement saying: "In addition to the painful ordeal of rape the young woman was forced to endure, she is now subjected to a second assault on her dignity (the video)."
The incident has highlighted the issue of rape in South Africa.
A recent survey suggested that more than a quarter of the country's men had admitted raping a female.
About 56,000 rapes were reported in the country last year although experts say many victims remain silent.
The suspects will be kept in police custody until the next hearing, the AFP news agency reports.