[Verginius Rufus]

If they can just locate a living person whose mother can trace her lineage entirely through females back to a sister of Joan of Arc (if she had any sisters) or to a sister of her mother or of her maternal grandmother, they can see if the mitochondrial DNA matches.

Of course, finding someone who can trace his or her genealogy so far back on female lines will be difficult...better set CBS to work finding the documentation.

[J_Baird]

Joan's siblings and entire family in fact were well documented and the family actually still lives in the same town she originated in. So they have DNA to test this against.