S5, E6: Katherine Rutherford walks out of her apartment and notices the elevator is out of order again. A man comes up behind and also notices. Being heavyset, it will take her a while to get down the stairs so she tells the man to go ahead of her, but instead he pushes her down the stairs, where she breaks her neck and dies. The killer breaks a necklace with beads to make it look like she tripped. The next day while checking out the scene, Stottlemeyer and Disher discover the beads. At the scene, they also discover a pin with the number '25' on it. Turns out that Katherine Rutherford is a nurse who worked at the free clinic in Berkeley where Monk also went to school.