Since then there have been a number of responses to this crime. In June the heads of some of the world’s biggest NGOs co-authored an op-ed for the Guardian decrying the risks associated with open defecation.

In September, the BBC reported on a new charity set up in India to increase access to safe sanitation.

Bindeshwar Pathak, the founder of Sulabh International, declared that “no woman must lose her life just because she has to go out to defecate,” echoing Prime Minister Narendra Modi’s own vow to end open defecation.

“We are in the 21st century and yet there is still no dignity for women,” he said.

I started my professional career as a water engineer and spent years in Ethiopia, Eritrea, Afghanistan and Angola focused on how water and sanitation interventions could help reduce poverty or mitigate the consequence of war.

But anybody brought up watching the US TV drama series, The Rockford Files, knows that all crimes, particularly murders, have three fundamental elements: motive, means and opportunity.

What the responses noted above have in common is that they studiously ignore the motive for these rape-murders and instead discuss only the circumstances that provided the opportunity.

The American business theorist Chris Argyris identified the issue of “undiscussability” as a key factor in reducing the capacity of organisations and businesses to perform effectively.

Organisations, he found, were unable to discuss risky or threatening issues especially if these issues questioned the underlying assumptions and policies of the organisation.

This idea also applies to states and communities. Which is why the responses to these heinous murders has avoided one of the most “undiscussable” issues in human history: the intrinsic violence of caste-based apartheid.

Caste-based apartheid

Arundhati Roy points out in The Doctor and the Saint that, “Poverty … is not just a question of having no money or no possessions; poverty is about having no power”.

Caste-based apartheid maintains the exclusion from power for hundreds of millions of South Asian citizens in a way that is of vital importance – both politically and economically – for powerful elements of society’s elites.

For example, caste-based apartheid underpins the ’camp coolie’ and sumangali systems allowing the powerful to enslave, with impunity, vulnerable workers, often young Dalit women and girls, for the manufacture of textiles and garments for northern hemisphere markets, and hence to derive considerable profits from their enslavement.

Making the issue of caste-based apartheid taboo provides it with a layer of political insulation: how can something become an issue if one cannot even give voice to the question?

The failure to engage with the issue of caste in South Asian society is a failure in the most basic principles of good development practice.

There has been, over the past decade, a growing discourse of development as a technocratic project.

That is an idea that poverty reduction is principally about the transfer of things to people who do not have things. Bill Gates has been a particularly powerful advocate of this. But effective democratic development is not primarily a technocratic, or even an economic, challenge. It is a political one.

Democratic community development should be about the empowerment of vulnerable and at-risk people. Sometimes the constraints on empowerment are material things.

But much more often they are social systems which aim to exclude certain people from inclusion in society and in poverty reduction measures.

If these are unaddressed by development processes then the development project itself is constructed on foundations of sand.

The Dalit leader B R Ambedkar’s words in relation to just revolution also pertain to just development: “What is required is a profound and thorough conviction of the justice, necessity and importance of political and social rights”.

But the challenge of caste-based apartheid and its “undiscussability” shows something more profound.

Development is also a philosophical project: it is about finding the cause of injustice and calling it by its true name.

Without this, the system retains its power to warp and undermine even the most well-meaning efforts towards justice.

The outside world does not well understand the South Asian codes for caste discrimination allowing the perpetrators greater leeway to continue with what they are doing guarded by silence, and by this incomprehension, from criticism by the international community.

And the enforced silence around caste-based apartheid now extends as far as the UK with this British government’s pusillanimous acquiescence to Brahminist lobbying by refusing fundamental protections of British law to British citizens who happen to be Dalits.

This cannot be acceptable.

And, if the human rights and development community continue to remain silent on the issue of caste-based apartheid then we will each have to accept some measure of responsibility next time we hear of crucified Dalits hanging from trees.