When a 999 call came in from Penelope Jackson's residence, claiming she had just stabbed her husband and was planning to stab him a bit more, the police were left horrified by her chillingly calm demeanour.Upon arriving at the scene, officers found David Jackson lying on the floor, bleeding to death.Despite the urgency of the situation, Penelope seemed unfazed, even urging paramedics not to help him.But why had Penelope stabbed her husband? Was it a desperate act of self-defense, or was it a cold-blooded murder?