Here is my theory on this one. Ok. In a tropical climate, such as Florida IS in the heat of the summer, decomposition would speed up. Now, as a body decomposes, on about the 2nd to the 6th day, depending on the temperature, the linings in the mouth and the nose liquify and ooze out in the form of decomposition fluids. If THIS were the source of the stain, then that would fit perfectly with the 2.6 days time frame (and that time frame was an approximation, and could have been a bit less or more). So, we have a baby in the trunk, possibly covered over by her blanket, but lying right there on the carpet in the trunk. We have the Florida heat speeding along decomposition and the oozing from her mouth and nose draining into the spot where she is laying. Also, at this point, there is rigor mortis. It sets in, it leaves and then sets in again. If she was as stiff as a board there would have been no way for Casey to "stuff" her inside of something, a bag, a box or a tote-whatever-it would have been next to impossible with her stiff like that. But on the 3rd day the rigor lets up, or on day 2.6 approx. and Casey gets her chance to place Caylee inside of something. I believe she took her out of the trunk using the neighbors' shovel and laid her on either a tarp or bags or plastic in the back yard. Then she wrapped her up tight as she could get her wrapped, and placed her inside of something else, now sealed up in plastic. Then she puts her back in the trunk for several more days or possibly a week or more, and then disposes of her in whatever manner she chose. The decomp that had leaked out would continue to cause an odor, and the body, although inside of a box and wrapped in plastic would also continue to emit an odor which would grow stronger by the day. Once she was removed the odor lingered and lingers still...