Suspended death sentences such as the one given to Gu Kailai yesterday are a measure Beijing has adopted in recent years to reduce the number of executions.
Article 50 of the Criminal Law states that if a convict does not "intentionally commit any crime during the execution of the reprieve", after two years the sentence will be commuted to life imprisonment, or 25 years if the convict "genuinely demonstrates major merit". Further reductions are also possible.
"There is no clear law to define the suspended death sentence; the judges can give this sentence as the circumstances may require," said Beijing lawyer Li Heping .
He said Gu's case was definitely one of "first-degree murder", but she received a suspended sentence for political reasons, because she and her husband, Bo Xilai , were important figures.
An article posted on the website of the Dui Hua Foundation, a non-profit humanitarian organisation based in San Francisco, predicted that Gu could spend as little as nine years behind bars.
Given that state media reported Gu had a "physical and psychological dependence on sedative hypnotic drugs", she would also be eligible for medical parole, according to the foundation.
Chongqing University law professor Chen Zhonglin said a convict could ask for medical parole after the two-year reprieve lapsed if the prison could not provide sufficient medical care, or the convict was unable to get around on her own. But he said that even in the best-case scenario, Gu would spend about 20 years in prison.
"Normally one may have their sentence reduced to 20 years for good behaviour after the two-year reprieve … the Eighth Amendment to China's Criminal Law last year increased the mandatory minimum time served for life sentences from 12 years to 17," he said.
The origin of a suspended death penalty - jianhou in Putonghua - can be traced to the Qing dynasty (1644-1911), when the system was set up in line with the Confucian view of merciful punishment and cautious imposition of the death penalty.
Later, when the Communist Party took power, Mao Zedong adopted the concept. In 1951, at the height of a movement to suppress counter-revolutionaries, he said those "who have done serious but not extremely serious harm to the state could be sentenced to death with a two-year suspension of execution". Mao's order became a national law that same year.
In recent years, senior corrupt politicians have been likely to receive suspended death sentences. Mainland media reported in 2010 that of 11 ministerial-level officials who confessed to corruption, seven received suspended death sentences and the others received life sentences.
Last year former Shenzhen mayor Xu Zongheng received a suspended death sentence after he was found guilty of accepting more than 33.2 million yuan (HK$40.56 million) in bribes.