david marshall must serve a minimum of 20 years behind bars for the murder of eni mevish , a 20-year-old student at staffordshire university .
the 68-year-old stabbed her in the heart , lungs and liver six months after they met because he was ` jealous ' of her other friendships , stafford crown court heard .
the pair are thought to have met around six months earlier when miss mevish , originally from manchester .