I agree. The case against Oswald needs to prove that he did the shooting.
Why would you venture to say that? Just because you think he did? You have to actually examine the evidentiary basis for that conclusion and you're left with an unscientific handwriting "analysis" of a couple of block letters on a photo of a microfilm copy of a 2-inch order coupon and an "order blank" printed from microfilm that is now "missing" showing a PO box box number that Oswald had access to with a serial number handwritten on the form at some indeterminate time. And a photo with a rifle that (despite what Mytton claims) cannot be proven to be be the same rifle.
Evidence? Sure. Evidence beyond a reasonable doubt? Hardly. But even if it was, you've already pointed out the problem. Showing that somebody owned a gun doesn't tell you anything about who fired it at the president.
Well, ownership is relevant because it connects Oswald to the murder weapon. A jury does not have to find he owned it beyond a reasonable doubt to conclude that he owned the gun. They only have to find beyond a reasonable doubt that he committed the murder. They could conclude that he likely owned the gun and use that as one of the many pieces of evidence connecting Oswald to the murder to ultimately find, beyond a reasonable doubt, Oswald guilty.
The ownership of the gun comes from many different sources and circumstances. Marina admitted that Oswald purchased a rifle at about the same time as the purchase from Klein's by "Hidell" and that he had told her that he used the rifle to shoot at Gen. Walker. She said the rifle was kept in the garage in a blanket. The rifle was not there after the assassination. No other rifle belonging to Oswald has ever been found. The rifle had Oswald's palm print on the stock. His prints were on the paper bag found in the SN. Marina admitted taking the backyard photo of Oswald with the rifle. Oswald was seen taking a long paper package that he told Buell Frazier contained curtain rods. No curtain rods were ever found, of course. Oswald denied telling Frazier this and said he took his lunch. A jury might have little difficulty concluding that was not a lunch bag and that it did not contain curtain rods.
On all the evidence, it is difficult to fathom how any group of 12 reasonable people could, at the end of the day, find that Oswald was not tied to that rifle found in the TSBD.
Finding Oswald guilty of murder requires more than that, of course. But there is ample evidence simply from Oswald's conduct after the assassination adding to the strong circumstantial link to the rifle. All the evidence, together, is more than enough to establish Oswald's involvement beyond a reasonable doubt. The similar fact evidence from Marina of the attempt on Gen. Walker, is just icing on the cake.