Where is the source please that he admitted in court that he had never seen Sheila fire a gun?
I think you will find that he said he had taken her target shooting, he does not say she fired a rifle at any target. Remember he was asked if she could fire a weapon...OK his answer was yes, he obviously thought she could. Its not beyond possibility, in fact it is likely that she could have. Whether Sheila did is debatable, that is why we are here today.
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The point of whether she could or could not fire a weapon is a possibility whether you like it or not. There is absolutely no proof that she could not, just like there is no proof that she could, but it is very likely that she did know how to use one.
Not firing a weapon does not mean that it is impossible to use one. Ruth Ellis had never fired a gun before but she used one to kill her cheating lover and did not miss.
How many people buy guns in America that have never fired a weapon before in their lives then suddenly one day they have shot someone...I'd say that could be a very high percentage. 
The first shot Ruth Ellis fired missed. Moreover the gun she used was a double action revolver, all she had to do was pull the trigger to operate it. Single action means you have to cock the gun before calling the trigger. Double action means the trigger operates the hammer without it needing to be cocked. She didn't even need to know how to open the gun to unload the shell casings and load more rounds in because she only expended the rounds that had been inside the gun.
In contrast the Sheila needed to learn how to insert the magazine, chamber a round, remove the magazine and to reload it in order to have committed the murders..
When you buy a gun you get a manual that tells you how to clean and operate it and also get instructions from gun dealers as to how it works. Even if you buy it off the street you likely would ask how to use it if you don't know how it works. Sheila didn't buy any guns though.
Jeremy's words are unambiguous:
She never fired the rifle before.
Yet he told police at the scene the day prior that she had fired it and all other weapons in the house. Even the most biased defender in the world had no way to refute tha the lied when he told police she fired the weapon. Why did he lie?
Because he wanted those at the scene to think she was a threat to them and also so that they would believe she did it when they found the bodies.
After hearing his relatives talk to police about her having no interest in guns and so forth he decided to go along with their claims and changed things to her just walking as he shot. But he didn't go walking around to shoot with the rifle he only used it for target practice so that was a lie too.
You are doing exactly what April said Jeremy defenders do, including her when she was one, ignore facts and evidence and excuse all his lies and claims that make no sense for no reason other than bias.
