How does Melinda's insistence on a DNA test to determine the rightful owner of the sheath backfire in the novel, The Address?

When Melinda and her boyfriend Tony propose that the brand-new technology of a DNA test be used to determine who is the rightful owner of the incredibly valuable sheath that was discovered in the Dakota basement, Melinda's plan backfires in a huge way. The DNA test later proves that she is not a Camden heir, but that Jack and Bailey are.