Few of apartheid's functionaries were so admired and despised at the same time as General Lothar Neethling, the founder of the South African Police forensics unit in 1971.

He has now died in Pretoria of lung cancer.

He was a leading member of the Afrikaans Academy of Arts and Science, which gave him a gold medal for his contribution to society.

He was a respected figure in Afrikanerdom who described himself as a staunch Christian.

He was a legend among police officers and received seven SAP medals.

Neethling, who had two PhDs, was widely regarded as a brilliant scientist.

But in November 1989 Neethling's dark side was exposed, and after that he was often referred to as South Africa's own "Dr Mengele".

(The connection to Nazi Germany had another side to it: Lothar Paul Neethling was born in Germany in August 1935 and came to South Africa as one of many German war-orphans who were adopted by Afrikaans couples at the time.)

In 1989 Dirk Coetzee, a former commander of the SAP's Vlakplaas death squad, spilled the beans in an interview with the anti-apartheid Afrikaans newspaper Vrye Weekblad.

He spoke in detail about Neethling's reputation as a "genius chemist" who had developed all kinds of "remedies" to use on anti-apartheid activists, called "Lothar se doepa" (Lothar's Potion).

Coetzee related how he had visited Neethling at home and in his laboratory to collect "knock-out drops" and toxins which he then administered to ANC cadres.

(The ANC had documented many cases where guerrillas had died mysteriously and were later found to have been poisoned.)

Neethling denied it, stating that he only ever did forensic work in his laboratory, and sued Vrye Weekblad for R1-million for defamation.

The court case lasted many months.

Apart from Coetzee's evidence, a secret agent of the security forces, Leslie Lesia, also testified that he was given some of "Lothar's doepa" to kill ANC activists in Mozambique and Zimbabwe.

Mr Justice Johan Kriegler accepted Coetzee's version of events, found that Neethling had lied in court, and dismissed the claim.

Neethling then took the judgment to the Appellate Division in Bloemfontein, where the judges declared they could not determine the truth, because both Neethling and Coetzee probably lied.

In a judgment that was labelled a blow for Press freedom, they found that the paper had indeed slandered Neethling.

Vrye Weekblad was ordered to pay him R90 000 as well as the legal costs.

This forced Vrye Weekblad to close down.

After the judgment a Cape Town prosecutor declared that Neethling had once boasted to him how he had developed a potion that would simulate a heart attack.

Another police officer said Neethling offered to give him a capsule that he could use to kill ANC leader Tony Yengeni by giving him a heart attack.

During the Truth and Reconciliation Commission's hearings on the former government's Chemical and Biological Warfare Programme in 1996, it became clear that Neethling was in fact the one-time mentor of Dr Wouter Basson, the head of that programme who had earned the nickname "Dr Death".

Neethling himself again denied that he had given Coetzee any toxins to use on opponents of the government, but admitted that he had experimented with mind-altering substances and other concoctions not in line with ordinary police forensics.

After the TRC hearings I laid criminal charges of murder, conspiracy to murder, perjury and fraud against Neethling at the Brixton police station. As far as I know, there was never a thorough investigation into his actions.

Dirk Coetzee, who to this day maintains that his version of events was "100% correct", said this week that Neethling was responsible for the deaths of many opponents of apartheid.

"His death is the best news I've had for years," he said.