An 82-year-old Spanish woman suffering from dementia has accidentally murdered her husband after she served him a cup of liquid detergent instead of coffee.

The 87-year-old man died on Monday (5 October) night after being taken to Hospital 12 de Octubre by an ambulance. An early autopsy suggests the man died of poisoning and not from natural causes.

The couple have a full-time carer provided by the City of Madrid, according to El Mundo. They live in the Usera district in the Spanish capital. The carer was busy with housework as the couple had their lunch. Upon noticing the man acting strangely, the carer sniffed the cup to discover the man had ingested liquid detergent.

Police have questioned the carer, who confirmed that the deceased man's wife was suffering from senile dementia. The carer said the incident had been accidental. Crime scene investigators have taken samples of the detergent for testing.

According to El Mundo, "no precautionary measure has been taken against her (the wife)" by police". It is being investigated by the Scientific Police Brigade in Spain and the homicide unit of the Judicial Police Brigade.