I am extremely confident that it will be possible to confirm that Sheila was holding the rifle left handed when she was firing shots off from the right handed .22 semi-automatic anshuzt rifle...
You can even see the angle at which the spent and bloodstained brass cartridgea were travelling away from the ejection port of the rifle, whilst Sheila propped up the barrel of the rifle using her outstretched right arm! For example, with Sheila poised and firing shots the inside of her lower right arm and her right wrist would be somewhat twisted exposing the very same areas which took the brunt of the ejected and bloodstained brass cartridge cases - Sheila Caffell fired the anshuzt rifle, and based on the total number of shots fired, bullets recovered, spent cartridge cases recovered at the scene, the shots she fired either wounded and or killed one and then all of the victims in turn!
Anyone can carry out a very basic test using a broom handle by holding it as though it was a right handed semi-automatic anshuzt rifle with the fingers of the right hand upon it against the imaginary trigger mechanism and the left arm outstretched towards the end of the guns barrel and of course safe in the knowledge that once you fire the imaginary gun, the spent cartridge case will be extracted and ejected from the ejection port on the right hand side of the gun, effectively in a trajectory taking the propelled brass casing away from you the shooter!
Practice this imaginary test using a broom handle or a mop, and know that the imaginary brass cartridge case may take a 45° to a 90° trajectory forward of the ejection port, and that the ejecting cartridge cases offer spiral out of control upon being propelled out of the gun..
Boom, boom, boom, boom, boom, boom, boom, boom, boom and boom - non of the correspi ding ejecting spent cartridge cases will strike any part of your body, because you are holding the imaginary right handed rifle using the fingers of your right hand on the trigger mechanism, with your outstretched left Armand your left hand to support the barrel of the gun!
Now, try the same exercise, but this time away hands and use the fingers of your left hand on the trigger mechanism, with your outstretched right arm and your right hand supporting the barrel of the imaginary rifle...
Boom, boom, boom, boom, boom, boom, boom, boom, boom and boom - on this occasion each of the extracted and ejecting cartridge cases will almost certainly strike some part or other of your outstretched lower right arm, and even your wrist, and if these cartridge cases had got blood on them, there would be a very strong chance that bloodstained straition marks caused by the cartridge cases coming I to contact with your body, this is because your outstretched right arm is infringing on the space normally required in order for the cartridge casing to escape unhindered from the ejection port of the gun...
That is precisely what happened during the shootings at whf..
Sheila used the fingers of her left hand on the trigger mechanism, and the lower part of her outstretched right arm, and wrist to support and direct the barrel at the time of each shooting!