The day before Emily Longley's death, her boyfriend Elliot Turner shocked friends by pretending he had "murdered her".
Turner told two teenagers he had smashed Emily over the head seven times with a hammer until he "heard her skull crunch".
Jasmin Snook, 19, told a jury at Turner's murder trial yesterday she burst into tears when she was taken in by Turner's lie in the early hours of May 6 after a night at club Klute.
The British court was also told that days before her death, Auckland teenager Emily slept with Turner's best friend.
Emily, 17, had sex with Luke Ashford shortly before she was allegedly strangled by Turner, 20, the son of a wealthy jeweller, in a jealous rage, a jury at Winchester Crown Court heard.