Woman was petrified after threat: witness

James Scott Church has pleaded not guilty to murdering Leisl Smith, whose body has never been found. (AAP)

A witness has told a judge she heard a young woman had gone missing soon after she saw her in a supermarket looking petrified and saying her life had been threatened.

"She was absolutely shaken almost like she had seen a ghost," Kelly Smith testified in the NSW Supreme Court on Friday.