My son's girlfriend moved in with my family when she got pregnant. She has been here for a year now and the relationship is not working out. I have asked her to leave but she refuses. The sherrifs dept. says that I cannot make her leave, I have to evict her. What do I need to do to evict her.

Going through the learning prosses of evicting my girlfriend of several years so I have the answers.
Even though there is no rent involved with the girlfriend, there is still a landlord tenant relationship under law. This is in California, as of Jan 1, 2006 only a 30 day notice is required. In this case it is called a 30 day notice of termination of tenancy. From 2002 to end of 2005 a 60 day notice was required for tenancies of more than one year, the law expired end of 2005. Ok, you serve the notice, have witnesses or also mail a copy so you have proof of serving the notice. If your tenant is still there after 30 days you have to do an Unlawful detainer action. It's like small claims court you are asking the judge to order them out. Hopefully about 20 days after the notice expires you will be in court having your unlawful detainer decided. If you win the judge will set a date give or take 10 more days for the sheriff to help your tenant move. This is the end, when the sheriff escorts them out of your property they are now legally evicted and to return on their part would be tresspassing.
In some of the communist jurdictions of California, such as Santa Monica or Berkley a 60 day notice may still be requried. Check up on this or you might discover this at your court hearing and have to start over. Brek