The United States and Britain have urged Kenya to push ahead with plans to draw up a new constitution, despite the murder of a scholar closely involved the increasingly fractious review process.
Raila Odinga says the killing was a "political assassination"
Professor Odhiambo Mbai was gunned down in his home last weekend in what a senior government minister described as a "political assassination".
Ten western embassies and the European Union have now issued a statement calling for "a thorough, speedy and effective investigation".
The killing of Mr Mbai threatens to destabilise the entire constitutional review, which has already become bogged down in the deep tribal and political divisions which lurk at the heart of this East African nation.
Mr Mbai came from Kenya's often marginalised Luo tribe.
Many fellow Luos believe his death was meant as a warning to their most prominent politician - the outspoken Minister for Public Works, Raila Odinga.
President Kibaki appears to be resisting attempts to reduce his powers
He has repeatedly described the murder as a "political assassination", although he told the BBC that he was "sure that the government was not involved".
The background to all this is the key question of how executive power should be divided up by the new constitution.
Mr Odinga has made no secret of his desire for the creation of a powerful prime minister's post - which he would occupy. But the ruling Narc coalition has made a dramatic U-turn.
Last year, when Narc was still in opposition and trying to hold a brand new coalition together, it supported Mr.Odinga's views.
But since winning December's election, President Mwai Kibaki - from the Kikuyu tribe - has had a rethink, and now argues that most executive powers should remain in his hands.
So, was Crispin Mbai's death related to this power struggle? It's not at all clear yet. But many Luos seem convinced it was, and tribal tensions in Nairobi's slums are dangerously high.
As for the constitutional review process, it is still limping along at a conference centre on the outskirts of Nairobi.
It should have been completed last year, before the election, but was scuppered by President Daniel arap Moi.
The new government promised it would be finished before this April.
But now there is talk of it dragging on into next year.
Well-informed sources say the Narc government is actively trying to scupper, or at least delay the entire process, which could otherwise be completed within a matter of days.
In the end, public pressure may force those involved to agree to a final document.
Kenyans have become passionately attached to the constitutional process during the course of three tumultuous years.
Many see a new constitution as a key instrument to root out decades of corruption and mismanagement.