I recently had a case that involved DNA testing. My client asked me to help her prove that she was the child of a recently-deceased man (who never married my client's mother). After a lot of fits and starts, we were successful. A few things I learned during the process:
1. In probate proceedings involving an out-of-wedlock child, you need to rely upon Sec. 2-2 of the Illinois Probate Act: "If a decedent has acknowledged paternity of a child born out of wedlock or if during his lifetime or after his death a decedent has been adjudged to be the father of a child born out of wedlock, that person is heir of his father...."
2. It's important to do your detective work. I was able to locate DNA of the decedent by contacting various hospitals, one of which had retained a tissue sample for the decedent from about 20 years prior to his death.
3. Exhuming a body for DNA testing is VERY expensive, in most cases prohibitively expensive. I was given a conservative quote of $15,000. Testing of existent samples is much cheaper.
4. DNA testing results can show whether the decedent is excluded as a possible father and, if not, the probability that the decedent is the father. This can be expressed two ways: as a percentage (like, "there is a 99.8% chance that decedent is person X's father"), and via what's called a "combined paternity index." The combined paternity index is just the inverse of the percentage -- a 99.8% probability that decedent is person X's father means a combined paternity index of 500 (99.8 = 100-[100/500]).
5. 99.8% (or a combined paternity index of 500 or more) is needed to prove parentage under the Illinois Parentage Act of 1984 (see 750 ILCS 45/11(f)).
