My friend just found out that his Dad''s girlfriend forged a will and is curious to know how long will it take before its taken to court after he meets

I am an attorney in California so I answer with California laws in mind. Of course each state is different but I suspect my plan would work in most states.  If I were in your friend's shoes I would just go ahead and file a probate as if there is no will. He doesn't have to prove it's a forgery until the girlfriend brings it to Court.  If she has the nerve to present the fraudulent document then it would be attacked at that time. I would hire a probate and estate specialist and not a general practitioner.  Good luck to your friend.  -John