[dighton]

Maybe I don't understand it? I'm under the impression that a sister,half-sister,or even a cousin would have DNA similiar enough to the mother to "pass".

It looks like you do understand it. If she tried to pass off an unrelated girl who looks like the one in Kohl's videotape, DNA testing would catch it. If, as you suggested, she tried passing off a sister's kid or something like that, perhaps it wouldn't.

I'm pinging a few FReepers who (unlike me) have some real knowledge of genetics.

-- dighton, caught way the hell out of his depth.

[Orual]

There are DNA tests, as everyone knows, that will determine maternity and paternity of a child. Although the sisters could be tested and proven to have the same mother, a sister could be eliminated as the mother of her sister's child, and as you said, a "bogus" child could easily be detected. There also are DNA tests to determine siblings, but they are not as reliable as the more common ones. These tests require, for better accuracy, the DNA from both the mother and the father and in most cases it simply isn't available.

This is my understanding, and any corrections, deletions, or additions to the above are welcomed.

[VadeRetro]

I'm not really the expert here, but I'll share what I know. You get half your active genome from your father, the other half from your mother. So do all your non-identical-twin siblings. You and your sibs are all mixed halves of your parents, but you're all unique mixes. You get your mother's eye color and your father's hair. Your sister gets your father's eyes, your mother's nose, and the hair color your mother carries recessively from her grandmother. The result is that you and your siblings may not have the same blood type, may not be able to exchange skin or organ grafts.

So it's possible that a child could have specific genes that can't come from her aunt, if anyone wants to sequence the entire genome of both individuals. But I bet the typical DNA test doesn't do that and won't be sensitive to that level of difference. I suspect a lot depends upon just what tests are done and how sensitive they are.