The prosecution could rest its case today in the San Diego trial of David Westerfield. An expert in animal D-N-A is expected to be among the state´s last witnesses. Joy Halverson of QuestGen Forensics in Davis says she will testify for the prosecution in the trial of the man accused of kidnapping and killing seven-year-old Danielle van Dam. A judge approved adding Halverson to the witness list during a hearing that was closed to the media and public yesterday. A gag order prevents Halverson or the prosecution from discussing her testimony in advance. But prosecutors have said they found hairs that could have come from the van Dam family dog in Westerfield´s house and motor home.