In RE5's Lost in Nightmares, after the Chris/Jill clash with Wesker ending with Jill and Wesker head-diving down the castle tower, Chris is left alone with a presumably "dead" Spencer.
You have to consider this: Spencer had INVITED Wesker to the Castle (as noted in the Butler's memos), meaning he had planned his own death. What he had not anticipated, was the arrival of Chris and Jill as well.
Surely, Chris, the man of the series who went out to destroy Umbrella and it's activities, creating a worldwide anti-bioterrorist organization over the years, would never leave behind a body of the man behind Umbrella (there's just no way Chris does not know of Spencer- he's been reading files on the old fart since RE1, and has seen enough portraits and online research post-RE1).
Surely his body must have had some importance? Why would he stage his own death by inviting Wesker himself? But the plan got forked; Wesker did "kill" him, but he got owned himself; leaving the fragile body to Chris and BSAA.
Perhaps they can tie this into RE6.
"The man who smiles when things go wrong has thought of someone to blame it on". PSN: ElusionM
it was a bit anti-climatic they way they got rid of the most evilest character in the series(well one of the founder of umbrella anyway),i wanna think he injected a slow acting version of the virus similar to wesker and he'll come back knowing wesker would get arrogent and fail his plan for the world,but maybe hes just dead and thats it
there are theories that it wasn't infact Spencer but a clone/body double, remember Spencer created a number of clones (Wesker children) also there is no info regarding what he was doing after Umbrella's fall.