There is a requirement that notice be given to the state within a shortened period of time (as short as 180 days) and a formal claim must be filed within six months and suit must be filed, usually, within 2 years if the claim is rejected.
THe claim would have to be on behalf of the child's "estate" (even though the child didn't actually own anything, the estate owns the right to sue) and potentially the child you haev adopted.
These cases, and I have been involved in several, are extremely complex because they involve not only torts but also state and federal civil rights issues. Most of these cases involve 20k-50k pages of documents that have to be gone through "with a fine toothed comb".
If you want this pursued then you need to immediately contact a lawyer. You can find one at www.lawyers.com and in the section for Area of Practice enter Personal Injury or Wrongful Death. That should give you two lists of lawyers in your area. At that point it is a matter of finding one with whom you are comfortable. They won't charge for the meeting and if you hire them they will do the case on a %.
If your question has been answered then I'd offer my best wishes to you and ask that you please not forget to leave a Positive Rating so I receive credit for my work. Of course, please feel free to ask any follow up questions in this thread. I want to be sure that all of your questions are answered.