Neil Clark was remanded in custody at Dumbarton Sheriff Court on June 12.
He was charged with the murder of his 70-year-old spouse, Francine, in Bearsden, East Dunbartonshire.
Clark made no plea or declaration to the charge during a private appearance in the dock. He was remanded in custody and was expected to appear in court at a later date.
However, the Scottish Prison Service yesterday confirmed the death of Clark, a prisoner at Low Moss jail in Bishopbriggs.
A spokeswoman said: "Neil Clark, 86, was remanded in custody at Dumbarton Sheriff Court on June 12th 2014.
"Police have been advised and the matter will be reported to the procurator fiscal. Next of kin have been informed and a Fatal Accident Inquiry will be held in due course."