then,Fairchild had a stroke of luck.Her case lawyer came across
a report in the New EnglandJourna1ofMedicine about Karen Keegan, a Massachusetts woman whose family underwent DNA testing to become organ donors because she needed a kidney transplant.The bizarre results resembled the Fairchild case - two of Keegan's three sons were found to be genetically unrelated to her.Baffled,Keegan's doctor spent two years trying to crack the riddle.The breakthrough came when other parts of her body were tested.Results from tests of her mouth,thyroid,and hair showed they contained two genetically distinct ce11groups.Keegan was a human chimera,a mixture of two different people.The same proved true in Fairchild's court case following further tests“I probably wouldn't have my kids today if my lawyer hadn't discovered Keegan's situation,”Fairchild said. “They wouldn't have known to even consider me as a chimera”
Human chimerism occurs when two fertilized eggs fuse in the
womb,creating a baby with two full sets of genes.Keegan began as twin female embryos that,for reasons unknown, joined.Bio1ogically, she is both mother and aunt to her sons,who only received part of her unique DNA makeup.0nly about30 cases of human chimerism have been documented worldwide,and scientists had considered it extremely rare.But now they are beginning to believe the condition is more common than previously thought.As genetic testing becomes more discriminating as well as more routine,more human chimeras may come tolight.This would threaten DNA's status as the gold standard in everything from paternity tests to forensic probes of plane crashes and murder cases.DNA material from a chimeric victim or suspect could lead investigators down the wrong path.Genetics expert John Butler of the U.S. National Institute of Standards and Technology says although such a mix-up would be very rare,it could result in“a situation where someone that really did commit that crime didn'flock like they had committed it”
Charles Boklage,a biologist at East Carolina University,says