The mainland has been asked to consider not executing Hong Kong people convicted of capital crimes.
The idea was suggested to mainland officials during talks on formal arrangements for rendition - the return of suspects - according to a senior security official.
'We have given our views including [on the] death penalty,' said the official, speaking on condition of anonymity.
'We have asked whether it was possible that the death sentence on convicted Hong Kong people would not be carried out.
'Mainland officials have given their response. But I can't tell you at this stage.' The official said the discussion had been held long before the Big Spender trial.
'The death penalty is just one of the many sensitive and complicated issues that need to be resolved before we can work out some rendition arrangements.
'It would be a bit optimistic to say detailed arrangements can be concluded in a year.' The Government is hoping that the agreement will cover three major aspects: the handover of fugitives, mutual judicial co-operation in criminal cases and the return of persons jailed abroad to serve sentences in local prisons.
It is understood that officials were most concerned about how to define 'crimes' to be contained in the rendition agreement.
The official said: 'Hong Kong people could easily get involved in some commercial disputes on matters such as taxation. What economic crimes are has to be clearly defined.' The Government was also keen to make sure people would not be penalised for expressing their views in the territory, it has been learned.
Security Bureau figures showed a total of 128 Hong Kong people wanted by local police have been sent back from the mainland since 1990.
The official revealed the mainland Government has made formal demands for the return of some mainlanders suspected of involvement in crimes on the mainland.
'It's all criminal cases. No political crimes. We have refused their demands because there is no rendition agreement. The demand [for return] has been suppressed because they know our answer to the requests.' However, the official said they would not follow the practice adopted before the handover on pleas for clemency for Hong Kong people facing the death penalty outside the territory.
'The United Kingdom opposed the death penalty. Whenever Hong Kong people were sentenced to death before the handover, [Britain] always appealed on their behalf for clemency.
'In principle, we will do it differently now. Unless there are special humanitarian and compassionate reasons, we will not make an appeal.' The official said they had passed a letter from the family of a member of the Big Spender gang, Chin Hon-sau, to the Guangdong Higher People's Court appealing for clemency.
'We acted as a messenger. But appealing on behalf of the family is a different matter.'