Not being a science or medical person of extensive experience, I get a loose grasp of this evidence bringing my understanding to this level: the swelling, bleeding, and clotting from the head blow, even though the skull damage was certainly life-ending, did take some time. So she couldn't have been strangled and then hit.
You might want to check out
the second link in this post at FFJ for an excellent youtube demonstration, which is animation of how these injuries play out. (Sorry, but the first link doesn't work anymore.) You can note the time stamps and see that time elapses as they slowly bleed and swell:
Forums For Justice - View Single Post - Weapon used on JonBenet's skull: golf club or flashlight?
Another piece of evidence which is important, if it's accurate--it came from Lou Smit originally, but I think it has been confirmed by Kolar and other sources since: JonBenet's urine was located beside the cellar door near the paint tray. Remember she had urine on her longjohn bottoms in the front, as well, which probably became wet after she had been cleaned up and redressed, then laid on her stomach and strangled, releasing her bladder at the moment of her death. Along with the carpet fiber found stuck to the chin of the corpse, and which matched the basement carpet, was a tiny chip of green paint that matched a tube found in the paint tray, as well. The shards of splintered paintbrush from the breakage of the handle lying at the same location on the carpet beside the paint tray indicate that is where the paintbrush was broken. Logically that would indicate it was used to penetrate the vagina there--whatever purpose you attribute that awful action to serve--and then broken to tie onto the ligature to pull it tight.
With the child's blood found on the pillowcase on her bed, I'm simply following the evidence:
1. The child could have been bludgeoned in her bedroom or nearby, then laid onto the pillow, where her blood-tinged mucous dripped onto it. That same blood-tinged mucous was found on her upper right shirt-sleeve, as well. So she was bleeding from the head wound on those two items before she had duct tape placed on her mouth.
2. Since the paintbrush was a part of the murderous ligature, and since the evidence indicates that she was placed by the paint tray where it was located, on her face and stomach, with the evacuation of her bladder at that location it appears that is where she was strangled and died.
3. She did die from strangulation before the head injuries killed her--do we all agree on that?
4. So she was bleeding from the head injury upstairs, then over a period of time before she was strangled in the basement--or that's how I see the evidence.
From everything I've ever read or heard anyone who works with head injuries say, they are all different and individual. But JonBenet could not have survived hers, and most medical persons believe she would have become unconscious immediately after the blow.