Nasen Saadi, who studied criminology, killed Amie Gray after she went for a seaside picnic with a friend

A 20-year-old criminology student with a fascination for knives has been found guilty of stabbing a woman to death on a Dorset beach after spending months plotting the attack and quizzing university lecturers about how a killer would get away with murder.

Nasen Saadi, who became obsessed with notorious crimes, repeatedly stabbed Amie Gray and her friend Leanne Miles on Bournemouth beach on a night in May. Gray, 34, a sports coach and a mother, was killed after a blade penetrated her heart.