A small legal case might determine if every father gets a genetic test for parenthood at birth.

Nina Montepagani always felt the entry under “father” was not literally true. “I felt like I didn’t belong anywhere,” she said recently. There had been clues: oddly similar names, family stories and a piece of paper with an address in Rome carried in Giuseppe’s wallet for decades.

The decision by the New York courts about whether to delete Giuseppe Viola’s name from the old birth certificate could help reshape one of the most rigid rules of American law: the presumption that infants born to married women are the children of their husbands. The law often changes slowly to catch up with ideas about family, and Mrs. Montepagani’s challenge offers a snapshot of one case that could help erode a rule that dates from a long-ago world.

Oh, and there is a 100 million dollar fortune at stake. But, seriously, paternity tests cost next-to-nothing, why aren’t they automatic?