Stephen Akinyemi was shot dead in a fight at the home of Arran Coghlan, 41, in Alderley Edge in February 2010. Mr Coghlan was cleared of his murder.
The Royal Courts of Justice heard Mr Akinyemi was allegedly a police informant.
The coroner ruled a new inquest would consider the claim.
David Mason QC, representing Mr Coghlan, said his client claimed Mr Akinyemi was an informant for Greater Manchester Police or the National Crime Agency.
He told the court Mr Coghlan had been under "intensive" police surveillance and there was "live monitoring" of his Cheshire mansion and workplace on the day of Mr Akinyemi's death.
"If the police - because of their knowledge and relationship with Mr Akinyemi - knew that this was going to happen and that he therefore was going to Mr Coghlan's address armed for the purpose of supposedly resolving this issue with Mr Coghlan, we submit that this is an issue that is highly relevant," Mr Mason said.
Coroner Bernard Richmond said he would consider if "the nature of the relationship between Mr Akinyemi and the police or state agencies was such as to raise the issue that the police knew the nature of what was going to happen on that day and tolerate it".
He said he would also consider if the police had "any knowledge or suspicion from any source" that the events "were going to unfold as they did".
Mr Coghlan told an inquest in 2011 that Mr Akinyemi pulled a gun on him and that it went off during a struggle in which he was stabbed several times.
Coroner Nicholas Rheinberg recorded an open verdict at the time after expressing doubt over the businessman's version of events.
The new inquest was due to begin on Friday but will take place in February 2017 for legal reasons.
A fresh inquest will be held into the death of a suspected gangster amid claims police may have known "what was going to happen", a court has heard.