In most simplistic terms the COA views as follows:
1) drawback would occur from Sheila's fatal wound
2) Sheila's blood would therefore be in the weapon if it was used without a moderator
3) the weapon was tested and found to have no blood inside from Sheila or anyone else
4) the moderator was tested and found to have human blood inside
5) that human blood was Sheila's
6) the moderator was found in the closet
This establishes the moderator was used to fire the fatal shot then removed by the killer and put in the closet.
You have to first recognize and understand the above in order to be able to try to attack it.
There are only 2 ways to attack:
1) to argue they were wrong and that drawback would not occur and didn't occur and that the blood was thus planted in the moderator
2) to argue blood was found in the rifle but the finding was concealed and blood was then planted in the moderator
These are the only 2 lines of attack that can be made to get an Appeal court to vacate the conviction on the basis of the blood evidence.
The defense has found no evidence to establish either argument though.