Elisabeth Rohm is the toughcracking detective Kate Lockley. She was introduced in the episode "Lonely Hearts", who was on the trial of a serial killer that Angel was also on. Initially, she suspected him of being involved with the murders, but was soon set straight by the evidence which mounted to free him. She soon discovered he was a vampire-with-a-soul and her relationship with him became very strained. Kate blames Angel for the death of her father, who was brutally murdered by vampires in "The Prodigal".
Elisabeth has now scored a role on another show, so it is unclear as to whether she will return in season two.
I could only find pictures of Elisabeth's role on "One Life To Live", so that is what is posted here. If there are any "Angel" shots released, they will be posted immediately.