beijing china prosecutor begin monday formal legal proceed disgrace senior politician sun zhengcai consider contender top leadership accuse corruption crimes sun abruptly remove post party chief southwestern metropolis chongqing one china important cities july replace chen miner close president xi jinping late month put investigation september party announce would prosecute corruption sun accuse leak secrets bribery abuse power brief statement prosecutor say begin proceed sun suspect bribery approve take coercive measure chinese legal term generally refer detention case proceed add without give detail sun expel parliament last month remove immunity prosecution enjoy member body chongqing perhaps best know outside china association bo xilai another disgrace former party boss city contender top leadership jail life 2013 dramatic corruption scandal possible reach sun representative comment since put investigation unclear allow retain lawyer next likely step sun put trial certain find guilty legal system control rule communist party challenge party accusations china start formal legal proceed disgrace senior politician