Lovers, Xia Xinfeng and Mao Ansheng, literally had the kiss of death when Xinfeng passed a capsule filled with rat poison from her mouth to Ansheng.  Ansheng died. 

Xinfeng had suspected Ansheng was cheating on her.  Supposedly, the couple had agreed that "if either one of them cheated on the other, he or she would have to die."

Xinfeng has been sentenced to death.