CAPE Town can boast many governance successes — indeed, the Democratic Alliance’s (DA’s) national electoral ambitions are based largely on the party being in a position to do so. But there is one area where the city comes near the bottom of the class: crime.

It would be misleading to call Cape Town the crime capital of South Africa, as per-capita figures for the major crime categories obscure significant variations across the city. It is still safer overall to live in a middle-class suburb of Cape Town than in Johannesburg, although the same cannot be said for certain townships.

There are also stubborn historic reasons for the persistent frequency of violent crime in parts of the Cape Flats, including an entrenched gang and drug culture. And, as the DA would hasten to point out, in terms of the constitution, policing is largely a central government function, so the buck for the high murder rate in a place such as Nyanga must stop with the police minister in Pretoria.

Perhaps it still will, despite Nathi Mthethwa’s determined efforts to avoid being held to account. The Western Cape High Court’s decision to dismiss his urgent attempt to close down the O’Regan commission of inquiry into policing in Khayelitsha should see its hearings continue over the next few weeks.

The commission was set up by Western Cape Premier Helen Zille and the African National Congress accused her of pursuing a political agenda. But, in fact, it was civil society organisations that motivated for an official inquiry into the causes of rampant vigilantism in the township and led the legal challenge to Mthethwa’s attempted interdict. And the Social Justice Coalition, Treatment Action Campaign and Equal Education can hardly be described as the DA’s bosom buddies.

The O’Regan commission is the democratic answer to the crime and policing questions some desperate Khayelitsha residents have responded to with deadly violence. If Mthethwa had the interests of ordinary South Africans at heart, he would not only welcome an inquiry into police behaviour and methods with open arms, but ask that it be extended to include crime hot spots nationally.

Meanwhile, there is hope on the horizon for Cape Town and South Africa’s stubbornly high crime rate, although it has an unexpected source. Analysts have long puzzled over crime trends in the US, once considered the crime capital of the world, because levels of violent crime peaked in the early 1990s for no apparent reason, and have declined since.

Former New York mayor Rudy Giuliani was a great proponent of the "broken-window theory", which holds that strict policing of petty crime helps prevent more serious crime, and he did not hesitate to claim the credit when crime rates dropped steadily during his tenure. A number of behavioural economists have also suggested that the legalisation of abortion in the US contributed significantly to bringing crime under control a generation later by reducing the number of unwanted children in poor communities, who might otherwise have drifted into a life of crime.

But now another intriguing theory is gaining currency, one that is supported by research not only in the US, but around the world. This holds that a primary cause of crime rates shooting up in the developed world from the 1940s and 1950s was the ingestion of lead from exhaust fumes, and that the worldwide drop in crime rates is a direct result of lead-abatement policies introduced from the 1960s.

The effect of lead on brain development and behavioural problems in children is well documented, and the correlation with crime levels seems to hold true without exception. The two graphs track each other almost perfectly, indicating that US toddlers who breathed in high levels of lead in the 1940s and 1950s were considerably more likely to become violent criminals in the 1970s and 1980s, and that the banning of lead additives at about that time lead directly to the drop in crime about 20 years later.

Since lead additives were eventually banned from fuel sold in South Africa only in 2006, we have a few years to go before we can hope to reap this social dividend. But hope we must.

• Marrs is Cape editor.