LOL, thanks for all the replies. I especially like the dead chickens, beer and cigarettes idea, I almost choked on my sandwich when I read that. When I showed the trailcam photos to my friend last week, he told me good work, now just Photoshop a dead chicken in that f.......ing dog's mouth!
And, I can't believe the reaction (or lack of one) that I got after catching her in a big fat lie, either.
About it being a light-colored dog - there was no blood, they looked like they were all simply shaken to death (or maybe squeezed). But, I find it incredibly difficult to believe that it didn't come home reeking of chicken manure (and its paws covered in it), since there probably wasn't a square inch of my run that didn't have pawprints, and it hadn't been cleaned in a long time (it had been rainy, too). She does keep it in the house most of the time, so I'm sure she would have noticed the smell. It probably pooped out feathers too, judging from the scene I found.
The bottom wire of my fence is neutral because it's too hard to keep all the weeds down, and from the tracks, it looks like it's also coming in under the gate (which I can't electrify). I thought about tying bacon to the hot wire in that spot though, that's what you do for bears.