You tried calling their cellular number but it has been disconnected. You tried calling their home phone but get their answering machine. All you have left of this person is their last known address. But you're not sure if they still live there or not. Can you still sue them? Can you still get a judgement against them if you're unable to physically locate them?

If you have the last address then send them a certified letter, stating your issue and request and your intent to sue, to the address you know with return receipt requested. If you don't know how to do this ask the post office.

When you get the green receipt back from the post office you will know that they got it and that the address is good. Add a sentence to the bottom left of the on the front of the envelope " address correction requested". If the person has moved the post office may forward the letter but they will also send you a notice of what the new address is. It will cost you the cost of the reply but you will know where the person is.

I have used this several times with success to track someone down who has moved.

Yes you sue them, a trained process server can normally find them

Hey Jeff, suppose the address is valid. But how can you be sure that the person you're looking for still lives there? What if the person moved and didn't leave a forwarding address with the post office?

Hi Chuck, what exactly is a trained process server?

Forget suing the person, how are you going to collect? When you sue someone, you only have to make a due diligence effrot to serve them. If you mail to their last know address or publish a notice in a local paper or other methods and they show up in court then you win a default judgement. But what good is that going to do if you haven't a clue where the person is? How are you going to collect if you don't know where they are or wherer their assets are? You would just be wasting your time.

A trained process server is just what is sounds like, someone trained to find and serve people.