the boyfriend of someone I saw is now demanding cash from me and will not give my name to the DA.  They are having some kind of domestic issue...What do I do?

I would just call a lawyer and see that they say

So he gives your name to the DA, so what?  Like the DA has time or the inclination to start some investigation into a misdemeanor in the past?  I don't think so.
Just my opinion
MVR

I have and am waiting to hear back.  I am a nervous wreck.

I know you are right, but it just so nerve racking....This guy is doing it to 300 people..

back when I was married and my wife didn't know yet.

Some provider I got too involved with went psycho on me so I called it off.

A few weeks later she's calling and leaving messages that if I don't keep paying her she'll out me.

I decided to ignore her and she never followed through.

But it sucked, royally.

I hope the lawyer provides you with something comforting.  He'll probably write the asshole a letter telling him to cease or face prosecution.  (Blackmail carries a ten year sentence in some states.)

(still not a lawyer)

I am waiting to hear back from the lawyer and I am sure that noting will come of it; but it is the uncertainity of it... I am sure my lawyer is going to give me unmitigated hell over it to top it off.. It does take the fun out of the hobby doesn't it.

Telling the DA would accomplish nothing since there's no proof...  oh, yes, the GF / provider is guilty too.  Is he suggesting he'll throw her under the bus?  Probably the creep stole her phone.  
The real danger is that he'd tell a SO.  Wives do not need proof!  Hell, wives don't need reasonable doubt!  

That said, save any communications from the creep and he could be busted for blackmail.  If he persists, involve your atty.
skb

Well, I am not married; so that is not an issue.  I have already involved my attorney

thanks

The DA will not be interested in pursuing a case against, but should be very interested in prosccuting a shake down artist.

The risk you run is not from LE, but if you are married, have a sensitive job, etc. If being outed is not a major issue for you, I would not be too worried. BTW don't be surprised if it turns out the lady in question is also involved, no way to tell with the information given just don't let your guard down.

Good Luck, I know at best this has to suck.

Oh, I almost forgot. Get a lawyer.

is to never ever give a damn. be calm. do nothing.

Agree to a meeting and have him videotaped making his demands and be sure to get specifics. While he's out, have his place searched and robbed. When he gets angry, tell him you had nothing to do with it but were the victim of his apparent enemies who taped the meeting and that they want 10 times what he demanded or they will turn him in for blackmail. As you apologize profusely, act as a go-between, setting up two money transfers, and after the first, give the original tape and the meeting location to the DA. Meanwhile, you can head for the Caribbean with his girlfriend.

Well, that's what I'd do anyway. Don't blame me if it doesn't work.

His job is to give you legal advice, he's not your spiritual advisor.

Besides, all lawyers hobby (the males ones anyways).  

He'll be cool with you.

I had to spill all the beans with my lawyer when I went through my divorce.

After that I asked him what he though about all of my hobbying.

His response:  You're just an average Joe, I have clients with several kids from over a dozen lovers.

I am very sorry that this is happening to you.  I'm just wondering how you know that he's "doing it" to 300 people?  Is this her client list? (shaking down everyone?)

This is a very excellant question.  Please let us know the result.
skb

Fight fire with fire. File a complaint against the blackmailer with LE.  Get as much doccumentation as you can.

This guy is playing with fire.  He'll be lucky if he doesn't wake up with a crowd around him.  Best of luck, I hope this guy gets his come upends.

Be sure to keep a record of where you are at all times, witnesses, etc.  So that when one of the 300...  or a friend of one of the 300...  runs this sorry sob over, you won't get it hung on you.
skb

I am pretty sure we are talking about the same person.  I would love to compare "notes" with
you about this person ASAP because the money was
due today!!!

that boyfriend has a lot more explaining to do than you do.

Tell him to give your name to the DA.  Tell him to make sure he spells it correctly.

The guy attempting to blackmail you is not very bright.  The DA will do nothing.  It is a misdemeanor we are talking about.  The DA could care less. And this guy's statement, even if the DA was interested, means nothing.  Unless he was peaking through the key hole, he has no direct evidence of anything.  

I had a guy from an adult resort in another country threaten to blackmail me one time.  He said he would tell my wife.  I said go ahead (my wife and I have no secrets).  He said he would contact my local newspaper.  I told him to be sure he spelled my name correctly so they would get the story right.

Nothing happened.  The newspaper could care less about me.  And if they did (I am not a high profile person), they would need more than his word to avoid a liable lawsuite.

If he calls you again, have some fun.  In a very calm voice say, "Please be aware you are speaking on a recorded line" and then say nothing.  He will probably panic.

And remember this, if you pay a blackmailer it shows him you are weak. He will then come back for more.  He will never go away as long as you are feeding him.  Blackmailers see their targets as piggy banks they can always turn to for cash.

After making my post, I had another thought.

The boyfriend may well have the larger problem. If he has accepted any financial support from his girlfriend (if she paid the rent, even once) OR he has ever been involved in her business in any way, he has committed the crime of pandering.

Pandering is: living off the wages of a prostitute or assisting her in the procuring of clients.  Now, this is not a misdemeanor like soliciting, but a big time felony.

Thus, the last thing he is going to do is contact LE.  The alleged misdemeanor he will try to hang on you is nothing compared to what LE will do to him if they can prove pandering.

If he calls again, you might want to remind him of the felony he is likely committing.

Just a thought (never will be a lawyer)