Am I required to contact the DA investigator left a card at my door.

You know how on TV they are always saying "you have the right to remain silent?" Guess what - you do!

No. You are not "required" to contact anybody.

Sometimes DA investigators will contact you related to an investigation against you. Sometimes DA investigators will contact you because you could be a witness in some investigation in a case they have against someone else. You do not need to talk to any investigator simply because he/she leaves a card at your door. If you think you are under investigation for any crime, it is not advisable for you to talk to any investigator/deputy district attorney/anyone without your attorney present (or at all!) The only person you should discuss any criminal matter that involves you (either witness or defendant) is your criminal defense attorney. My response to this post does not create an attorney-client relationship with the poster.

You are not required to speak to the DA. If you want to know what it is about, hire an attorney or call the DA yourself.

You are under no obligation to talk to them,return their call,or answer the door, unless your curiosity is larger than your need for privacy

No. Yes. Maybe. If you really want to know what's up without speaking to the investigator, then you should retain counsel to determine what it's about. Not uncommon for people to have an attorney call the investigator back to determine whether or not they want to speak to the investigator.