Well the blood trail didn' t start for a good while, but, when we picked it up, we were getting different sign from the blood. There would be a spot of blood about the size of a cigarette pack which would be bright red with a few bubbles in it, but, then there would be about 10 feet of nothing and the next spot would be a small drop of very watery blood. Well, the trail did this for awhile, and finally it just turned into small bright drops of blood every 15 feet or so.
This sounds as if the deer was gutshot and " exited" out the rear quarter. The watery blood would indicate rumen/intestinal fluid. The bright blood would indicate muscle. Probably getting bubbles from expelled air out of the digestive track.
Also assumed based on the " hit back and high" scenario. Assuming he was in a tree, smacking the rear quarter probably left the arrow in the deer with a high entrance wound. Unless you hit the dorsal aorta running along the spine, there will be little blood. But with the watery blood and a back hit, the deer is down & done, especially if your friend was shooting at a downward angle.
S&R