Kendall Jenner says she was terrified by a man who followed her into her driveway earlier this year and repeatedly knocked on her car window in the Hollywood Hills.
The model and reality television star testified at a stalking trial that it was the scariest moment of her life.
The 20-year-old Jenner testified that she previously saw defendant Shavaughn McKenzie outside her former condominium in Westwood.
Jenner testified for about 50 minutes and is due back on the witness stand after a lunch break.
The 25-year-old McKenzie is charged with misdemeanour stalking and trespassing. He did not show any emotions during Jenner's testimony and at several points looked away from her.
A defence attorney told jurors McKenzie has a severe mental disorder and was simply trying to talk to Jenner.
McKenzie is charged with stalking and trespassing at her Hollywood Hills home, where he was arrested in August.
McKenzie could face up to six months in jail if convicted of either charge.
Shelli Azoff, a family friend who Jenner called for help, testified that Jenner was screaming and crying after seeing a man outside her car.