Paul Simpson had reason to suspect that he wouldn't like the results even before he took the paternity test. Another man had confessed that he was the father of the two children born during Simpson's marriage.
Still, Simpson said, he had hoped that at least one of the children would turn out to be his biological child. The DNA test showed neither was.
"It's hard to describe how bad I felt," said Simpson, 25, who divorced the children's mother. He was angry, then severely depressed. But he did not regret taking the test. "I had to know if they were mine -- I had to."
DNA tests to prove or disprove parentage are becoming more common and easily accessible. Do-it-yourself kits are available online for about $200 -- although those results aren't admissible in court. Professionally administered ones -- which Simpson used -- cost about $500.
But family law experts warn that the tests, although answering some questions, raise more. The ability to determine a child's biological parent with near certainty is creating quandaries for lawmakers about what is best for children and what exactly makes a father. Is it strictly biology, or does acting like a father make you one?
"It's a really tricky, nuanced question," said Stephanie Walton, an expert on child support with the National Conference of State Legislatures. "How do we culturally and legally as a society catch up with the technology?"
The technology offers a chance for dads who are paying child support to learn with certainty whether the offspring are truly theirs.
Over a 10-year period, the number of DNA tests for parentage more than doubled, to 390,928 in 2004, according to AABB (formerly the American Assn. of Blood Banks).
Those 2004 cases include paternity tests, prenatal and postmortem evaluations and immigration tests intended to prove that a mother, father or sibling is related to the person he or she is sponsoring for a visa, the AABB said.
But there is no federal regulation of relationship DNA tests or their marketing to consumers, said Eduardo Nunes, the AABB's director of standards and international affairs.
In Simpson's case, Illinois, like most states, presumed him to be the father because the children were conceived during his marriage. Under state law, he had two years from finding out that he wasn't the likely father to challenge that assumption of paternity. The children were both under 2 when he had the test.
Chicago lawyer Jeffery Leving, an advocate of fathers' rights whose firm represents Simpson, said his case was not uncommon. Leving opposes the two-year time limit. He said "paternity fraud" -- when a woman tells a man he is the father although there is a possibility he is not -- hurts children, men and families.
Paternity tests a man's DNA to tell, with 99.9% certainty, whether he is the biological father of the tested children.
Labs reported an exclusion rate of 26.8% in 2004, according to AABB data. The organization says that does not mean that all of those excluded men were misled into believing they were biological fathers and later found out they were not. In some cases, several men may have been tested, though not all were told they were the father.
Meanwhile, laws regarding paternity vary widely.
Some states allow fathers to challenge paternity at any time, whereas others forbid husbands from challenging paternity. Others have time limits or restrictions.
A key issue is whether the man signed a voluntary acknowledgement of paternity, which is important when the state is trying to get reimbursement for public aid.
Melanie Jacobs, an associate professor of law at Michigan State University, argues that concern for children should be paramount. The law should not permit men to challenge paternity at any time because it could harm children, she said, adding that she thinks the law needs to be more consistent.
Indiana University professor Michael Grossberg, who studies the history of family law, said he was especially troubled by situations in which a man has been living with a child he believes is his, then decides after a DNA test that he no longer will have a relationship with the child.
"Blood is only one definition of fatherhood," he said.
In the June 2006 issue of Current Anthropology magazine, researcher Kermyt Anderson, a University of Oklahoma anthropologist, found in a review of paternity and genetic test data that only a small percentage of men were deceived into thinking they were the biological fathers of children they were raising.
Anderson said these figures rebut so-called conventional wisdom that 10% of fathers are unknowingly raising children not biologically theirs.
For those who do learn they are not the biological father, what they do epends on several factors, including what his relationship is with the mother and how long he has suspected that he may not be the father.
Some men in this situation say they're being defrauded. They call themselves "duped dads" and say they don't want to be ATMs for others' children.
Carnell Smith of Georgia is one of the leaders of these dads. He pushed Georgia legislators to change the law so that a man who is under court order to pay child support can challenge paternity at any time.