South Africa has had 52 serial killers since 1990 and is one of the top three countries for such crimes - but it has had the most success in catching the culprits.

The fall of apartheid, like the fall of communism in the Soviet Union, had been accompanied by significant social change that provided fertile conditions for such crimes, Gerard Labuschagne, head of the police Investigative Psychology Unit, told a media briefing.

Lending support to this conclusion is that in the years between 1936 and 1990 there were eight serial killers.

The high number since 1990 has ranked South Africa with Russia and the United States.

Sixteen of the killers in South Africa have not been caught, but the country has the highest arrest rate. The average time taken to arrest serial killers is six weeks, whereas the international average is two years.

The SA Police Service trains detectives around the country to assist Labuschagne's team of 22 in their investigations.

South Africa has been alone in training detectives to help apprehend serial killers and the the Investigative Psychology Unit's headquarters in Pretoria has given training to detectives from Britain's Scotland Yard, Germany and France.

Since the 1930s, 489 people in South Africa have been slain by serial killers. Among the most prolific of the killers arrested has been Moses Sithole, who murdered 36 women in Atteridgeville, Gauteng. He is serving a sentence of 2 000 years.

In other countries, serial murderers are almost exclusively white males and their victims white women, but increasingly in South Africa such killers are targeting people of all races.

Muti murders are also being considered a serial crime, Labuschagne says.

Detectives have found muti on a growing number of cash-in-transit robbers.

"The difference between normal crime and serial crime is that normal crime is most often motivated by financial gain, whereas with psychological crime the crime is the need," said," said Labuschagne.

Psychologically-motivated crimes included serial murder, serial rape, infant rape, muti murders, sadistic murder, extortion and murders with "bizarre circumstances".

The chances of rehabilitating serial murderers were too small to even consider.

Once they were in jail, however, serial killers became model prisoners because they could function in a strict environment with set rules.

But they did not have the "mental capacity" to function as normal human beings outside prison.

All serial killers "are almost relieved to be caught so they can share their stories".

It was a myth that they were abused as children, said Labuschagne. Sithole, for example, had begun killing women after being convicted of a rape he said he did not commit.

"The conviction for a crime he claimed never happened could have turned him against women."