In CA you can break your lease. Then, you can only be charged rent until the LL finds a new renter, and he has to make a reasonable effort to rent the place. My understanding is that the court in CA assumes 30 days should be plenty.
So, give your notice. Include in the notice the list of days and times that you complained and called the police. Then say that since the LL didn't take care of the problem, you don't expect him to charge you any further rent beyond your 30 day notice. In return, you won't sue him for loss of quiet enjoyment.
BTW, Constructive eviction would be the LL not taking care of the problem, basically causing you to move out. That's what a constructive eviction is. You declaring the place unlivable is when a place is uninhabitable - I think that's what you're referring to. They're different. What you could do is sue for the landlord's breach of the Covenant of Quiet Enjoyment. Here's a link about it from a CA law website:
Quiet Enjoyment | Tenant Hub
Here's a link re: breaking your lease in CA:
http://www.nolo.com/legal-encycloped...hapter9-5.html
This is what I propose you write - something like this:
Dear LL:
This is my written notice that I will be vacating my apartment at ________________________________(address) in 30 days, which will be by midnight _________________(count 30 calendar days).
I am vacating the unit prior to the end of my lease because you have breached the Covenant of Quiet Enjoyment, which is written in my lease (see if it is, if not don't say that part), as well as implied by law in California. You have done this by neglecting to deal with the tenant in unit ______________, who has been severely disturbing me and other tenants with loud noise, yelling, and frightening verbal confrontations. I, as well as other tenants, are now living in fear of this tenant.
I have complained to you on these dates:____________________________. I have phoned the police on these dates____________________________. And still, you have not addressed the issue.
I am willing to absorb the cost of moving, and in return I expect you will not attempt to charge me rent beyond my move-out date, and consider my lease terminated by agreement with no penalty. I will leave the unit clean and undamaged, and also expect to receive my full security deposit.
I also expect you will give me a good reference regarding my payment history.
If these terms are not acceptable to you, and you attempt to collect rent beyond my move-out date, and/or keep any of my deposit beyond what is allowed by law regarding damage, or affect my ability to find new housing, I intend to seek remedy to the full extent allowed by law.
I will notify you of my new address prior to my move-out date.
Sincerely,
You
Send it with proof of delivery. You can email it, and send it priority mail with delivery confirmation.
Then, deal with him after you move, if he tries to come after you for more rent or keeps your deposit, etc.
Good luck. What a pain.