It sounds pretty clear that the closing attorney made a mistake and that you owe the tax. I would pay the tax and forget about it. You will sleep better.

The right thing to do is pay the back property taxes. You signed affidavits at closing stating that your condo was free and clear of all liens. Even tho the title company
inadvertently missed the back taxes it was your responsibility to mention at closing.

Your question regards "legal" responsibility and does not ask about the more important question of "moral" responsibility. Did you own the realty for the period that the taxes cover? If so, you should pay your taxes. Not acceptable to saddle the new owners of the property with your tax debt. Unless of course somehow the tax debt was disclosed as an offset of some type. I am not an attorney just trying to follow the logic of your question which would otherwise seem to have a simple answer: pay the bill.

Yes, simple and straight forward answer.

Pay It
 

Let's see, what's the worst that could happen it you paid it. You'd be paying a debt you incurred. What the worst that could happen if you don't pay it. Collectors, aggravation, maybe a judgement, a negative on your credit, legal fees if you want legal advice, more aggravation. So, if you have the time and stomach don't pay.
If I'm not mistaken Title Insurance covers the buyer. If they find liens later then they pay or correct them. It doesn't protect the seller. So, read your documents carefully. If you cannot find something obvious that excludes you from liability then I'd pay but again, if you like drama don't pay and go for it.

I would say your liability is to the taxing authority not the title company. The taxing authority will be the ones that come after you. They will get their due.

Paying taxes missed by the title company
 

Are you honest or not ? If honest pay what is rightfully your bill.

taxes
 

If you look through the reams of paperwork you signed at closing you will find a "Tax Re-Proration Agreement" (or something close) that states that the closing agent is not liable for additional taxes. The actual taxes is different then stated will be adjusted between the two parties. You will owe something, just pay and move on.

Did you pay for title insurance during your sale? If you did that is on them not you.

This is an easy one: If you have any morals, you will pay it because you have an obligation to pay it.

you best pay it or you'll be living in the boxcar!!!

Maybe
 

The Title Ins may have paid the tax so that their would not be a lien on the property. This is what the insurance is for. If not they could have simply ignored it and let the taxing authority go after the seller. IMHO

If they overcharged you, would you expect a refund? I assume you would, so this would just be the reverse. Pay what is owed.

Real estate taxes
 

Your property, your taxes, your debt and their mistake. Pay the tax and ask the law firm to pay any penalties and interest since that would likely be their fault.

Buyers pay the TI, sellers do not