LONDON – A jilted and jealous British woman was sentenced to at least 30 years in prison Wednesday for the January murder of a woman she considered her love rival.

Sarah Williams shot 60-year-old Sadie Hartley with a 50,000 volt stun gun when Hartley answered the door of her home in northwest England in January, then attacked her with a kitchen knife.

Prosecutors said 35-year-old Williams had previously had a fling with Hartley’s partner, Ian Johnston. They said after he left her Williams continued to exchange explicit texts and photos with Johnston, while plotting the “perfect murder” of Hartley.

Williams and accomplice Katrina Walsh were convicted by a jury at Preston Crown Court after a seven-week trial. Both had denied murder and blamed each other for the crime.

Prosecutors said Walsh, a 57-year-old horse riding instructor, was not present for the attack on Hartley but participated in 18 months of planning that involved travelling to Germany to buy the powerful stun gun, which is illegal in Britain.

Judge Mark Turner sentenced Williams to life with no chance of parole for 30 years, and Walsh to at least 25 years.

“Let no-one believe this was a crime of passion,” the judge said. “It was a crime of obsession, of arrogance and of barbarity, but above all a crime of pure evil.”