The number of executions in China is a state secret, but it's estimated to be around 5000 per year -- more than all other nations combined.
Bodies of executed prisoners have long been a major source of organ transplants in China: http://en.wikipedia.org/wiki/Organ_transplantation_in_China
According to several reports, political prisoners and prisoners of conscience (e.g. Falun Gong members) are being executed in the thousands and harvested for organs. These are not convicted murderers, but people who have never even received a trial.