Alex Verdu Munoz had been charged with murdering 68-year-old Valerie Freer, who died of neck injuries in the village of Whittington, near Lichfield, on February 24.
He was awaiting trial but was pronounced dead on May 15 at HMP Strangeways in Manchester, Staffordshire Police said.
Munoz also faced charges of aggravated burglary, burglary, possession of a bladed article and dangerous driving.
The case was listed at Stafford Crown Court for a hearing on Monday. The court confirmed the case against him was officially closed.
Valerie Freer was found on the driveway of her home by paramedics at around 10.53am.
In 2014, one of her dogs, a Samoyed named Dan The Man, was runner-up in the Best in Show category at Crufts.
His death is not being treated as suspicious.