Reuters
Gu, the wife of top Chinese leader Bo Xilai, was convicted of murdering British businessman Neil Heywood in 2012 and given a suspended death sentence.
Prosecutor Man Mingan was appointed to the case in 2012, taking part in one of China's most dramatic court cases in decades.
So far, police are saying the 60-year-old Man committed suicide but are still investigating the death. Some state media also reported that the Communist party had a meeting to discuss his death.
Gu is the daughter of one of China's most important revolutionary generals. Her husband, Bo Xilai, is a once powerful member of the politburo in China and potential candidate for promotion to the top of the Communist party, whose downfall is directly linked to the murder case.
Bo, the son of one of China's revolutionary founding fathers, is now serving a life sentence for corruption.
REUTERS/Jason Lee
The poisoning of Heywood was made public after a former chief of police - who initially helped cover up the murder - alerted US diplomats out of fear that he would be killed himself. The murder took place in the city that Bo served as Communist party secretary.
Gu's trial was held in Hefei, which is far away from any areas that be under her husband's influence.
The Financial Times notes that "the outcome was decided beforehand by senior political leaders" and media could not freely cover the highly politicized trial.
After the trial, Man who had been thrusted in the center of public attention, received a special meritorious award for how he handled the trial.