I actually asked this question of a medical examiner: Do dead bodies bleed? His simple response: NO. Now before you all go pointing to some t.v. program or some crime scene photo, remember a dead body will leak blood from the wound while the natural processes after death continue. But dead bodies do not bleed. At least this is what I was told. Maybe the guy I talked to does not know his stuff and with all this online sleuthing, I have definitely gotten things wrong before. Anyone can correct me.
What the medical examiner was explaining to me was that in order for your body to "bleed" blood you have to have blood circulation. When your heart stops pumping you do not have blood circulation. Someone who is actually a medical expert can explain this better than I can.
So in this case I would suspect that the majority of the blood in the trunk was J.B. Beasley's. And yes, if there was enough blood to leak onto the undercarriage of the car, she probably was alive for a while. How long is anyone's guess. It would be a good question for an M.E. Based on the wound, her weight and size, how long would it take for her to lose enough blood and pass away? If she was actually found in a sleeping position in the trunk, it might also mean that the order of shooting was Tracie Hawlett first, J.B. Beasley second, given that if the killer saw that she was still alive might have then finished her off. It could also be that the casing from the bullet that killed J.B. Beasley was the one on Tracie Hawlett's leg. How he did not see the bullet casing was strange, especially if he was a police officer, but maybe the guy has some problem with his eyes.
I think I could be wrong about one thing. Before I wrote that maybe the killer waited to move the car. That could definitely be wrong. In order for the blood to actually form a trail under the car that would mean that it had not yet coagulated. So there is also the possibility, at least based on this online evidence, that not only was J.B. Beasley alive, but that she was alive while the killer was driving the car to the spot on Herring Ave.
So I hope this information helps, at least in terms of understanding blood loss, blood hardening, and how it contributes to a time frame associated with the case of J.B. Beasley and Tracie Hawlett. Every crime scene tells a story. You just have to look for the clues to understand it.