yes but .22 calibre is very low not high. I found similar claims in other forensic books about relation to calibre, barrel length and backsplatter that you criticised me for just making up. They first done some experiments in 1977 on this but I cannot find more information it 
The link I provided is one on googlebooks. Googlebooks brings me up a limited PDF of the Book. does it really matter? what difference does it make
The publication from 1977 is the seminal work on drawback. Their research determined that in large caliber weapons blood was found up to 5mm deep when the gun was fired at distances up to 5 inches from the target. (With the gun fired 5 inches or less from the target some blood was able to get up to 5mm inside the barrel). For .22 rimfire weapons blood could get up to 5mm deep when fired up to 1.5 inches from the target. At contact ranges the blood was able to go much deeper than 5mm but still only would travel several inches. I cited this 5mm figure a number of times the past week but forgot where it ultimately came from until earlier today. A sizable number of sources cited the 5mm figure that came from their research.
If you research backpatter and drawback which is simply a sub category what you will find is that the most critical factor of whether backspatter occurs is the location of the wound. The attributes of the skin and blood vessels in the location of the wound is critical to whether there will be blood expelled. The caliber and type of round is another factor that ties in with location. Certain locations such as where her neck wound was will result in spatter regardless of the caliber of the weapon. In contrast other locations such as the head are unlikely to result in spatter from .22 caliber weapons, it happens but not that often.
where the spatter lands depends on how far away the shooter is. If it is a contact wound the blood will be sent several inches into the weapon. How deep depends on the weapon it can travel 5 inches with a larger caliber but only 3 with smaller caliber weapons. At non-contact ranges it can travel several feet and a small amount can get inside the barrel in addition to on the gun and shooter. but it will not travel much beyond 5mm inside the weapon at non-contact ranges and even then it has to be at close range. If the shooter is too far the spatter won't even reach the shooter.
What should the defense have done:
1) have a medical/firearm expert assess the prosecution expert's claims that Sheila's fatal wound was a contact wound
2) have a medical/firearm expert assess the prosecution expert's claims that the location of Sheila's fatal wound would be virtually certain to result in backspatter based on the nature of the skin and blood in that area of the body and what the wound did
Did the defense do this? Presumably but who knows since we don't have access to the full defense file. On appeal the defense has not found anyone to refute that it was a contact wound or that it was virtually certain to result in backspatter.
At this stage they need evidence that her wound would not have resulted in backspatter. It's not good enough to say it might not have. They need to prove it would not have in order to be able to suggest that is proof the blood got there by some other means. If they couldn't do that through the use of new evidence they would have to use that as the basis of a clemency petition.
But the location of her wound clearly was a location where the kin and blood flow were ideal for backspatter to occur so it is obvious why the defense has to this day been unable to come up with any evidence to establish backspatter wouldn't occur.
That forces the defene to try attacking the blood in a different manner.
