Okay, so we seem to be in complete agreement about how the math works out. If so, then I'm confused as to why you object so strongly to the prosecution's argument on purely mathematical grounds; I haven't read their argument myself, so it's entirely possible that the argument itself is weak in some way, but I think that right now we're just talking about the math.

If we ignore their specific language, the plan of coming up with ~20 pieces of moderate evidence is a perfectly reasonable strategy for correctly establishing guilt, assuming that there is absolutely no mitigating evidence. Your complaint seems to be that they use different language/notation than you and I do to talk about evidence, which seems hardly fair.

Although I would also note that since humans are bad at intuitively distinguishing between moderate evidence for and moderate evidence against a hypothesis, trying to find many pieces of weak evidence is probably not a good strategy if the goal is to get humans to correctly decide the accuracy of an assertion.

ETA: By the way, I've been working under the assumption, based on the tone of the original post, that you think there are serious mathematical flaws in the prosecutions argument. If that's not the case, and you just wanted to use this case as a point of illustration, then I apologize for the confusion.