[SilverSyko]

Originally Posted by rogerpepitone

What sort of forensic analysis would be necessary? Mion has a tattoo; Shion doesn't.

I wouldn't be so sure about that.

Spoiler for Watanagashi-hen/Meakashi-hen:

Near the end of Watanagashi-hen when Keiichi and Rena met with Mion, who was really Shion, she told them about the demon tattoo. Shion almost stripped to show it to them until Keiichi stopped her, but otherwise she didn't look the least bit hesitant.

So my theory is that both of the Sonozaki sisters have a tattoo. Of course the one possiblity that blows this theory out of the water is that Shion was HOPING they would stop her.

So with both having the same tattoo, the only other way to tell the twins apart is through forensic testing. Mainly from fingerprints/footprints as those are different even between identical twins.