erm - the death penalty used to be enforced in this country for petty theft. there was still petty theft. America has a vastly higher number of murders per capita than the UK - that is partly to do with its gun laws, partly to do with the third-world level of deprivation some of its citizens are subjectd to, and partly to do with being an alien culture in a less tangible sense: it is a more violent place.
there is no evidence the death penatly has any preventative effect - plenty of evidence to sugest it is only enforced agaist the poorest, least advantaged criminls in each society where it still exits.
the way China enforces the death penalty is entirely to do with the governmnt wanting to make a point about something - therefore it is unpredictable. In the case of the university buildings that collapsed - the vice-chancellor was executed - the chancellor was not (i think, he was rather better connected)
same in the melamine milk scandal high ranking officials were executed, but the highest were not.
the whole way China works is about the relaionship of the government with is own population, nothing to do with international concerns, nothing to do even with its own laws. They will have a head for puplic relations effect, but not the head of the guy who has guanxi within the party.
i will add a story from the dark ages in china - a female tourist had her wallet stolen on th train. At the next stop a policeman drags a man in front of her asks 'Is This Him??'
she says yes. The policeman drew a revolver and shot the man through the head point-blank, leaving him dead on the platform.