DNA evidence has lead police to a murder suspect after 13 years of investigations.
Occurring in 2004, so-called crime of the churrero saw an elderly couple killed during a burglary at their Chiclana de la Frontera home in Cadiz.
The severity of the violence caused instant death to the man and serious injuries to the woman, who died several months later as a result of the brutal robbery.
Four people have been arrested and are believed to have belonged to an international criminal organisation of Eastern-European origin that has operated for more than 15 years in several European countries, specialising in robberies.
The group consisted of roughly 30 people with violent backgrounds and criminal records across a number of European countries who, at the time, had been operating in Spanish provinces, using fake identities to cross borders.
One of the members reportedly had 13 different identities in Spain.
Investigators travelled to France and Austria to arrest two of the suspects as part of Operation Algorithm.
A small blood trail was left on a wall which a burglar had climbed during a recent robbery which has enabled police to link it forensically to the mid-noughties murder, placing the accused at the scene of the attack.