Mystery swallowtail...do you know?

Unidentified butterfly sipping from purple cone flower.

Photo by Richard Weigand.

Richard captured this scene in the SW Virginia Blue Ridge. I'm having a difficult time figuring out what kind of butterfly it is from the angle presented, but there may be enough visual information there to do it. Do you have any guesses?

Two things that caught my eye right away were the bold blue markings and what appears to be two tails on each hind wing. Could this be a female tiger swallowtail?...a spicebush swallowtail?...other? Help!

Sid-by-side butterfly comparison resource, as provided by comment below:http://www.naba.org/chapters/nabambc/common-comparisons.asp