You are making a massive assumption.. That the person who told amaral about CB thought he was a patsy.
The PJ knew CB was being investigated... This was leaked and it was Amaral who came up with the ide of a patsy... Is far more likely imo. I think the idea of the Germans supplying a patsy is daft.. I don't see any reason they would do this
I think the term is being used out of context. This 'patsy' is actually just not the nonce you are looking for (because he doesn't exist). Not a patsy in the sense of the word as we know it, someone just to pin the blame on, but Amaral had the other part right; convenient. In the wide vicinity of the right place at the right time. Nonce, yes, thief, yes, actually did it, no, that's pretty obvious now.
Circumstantial evidence is dependent upon cogency on the unlikelihood of coincidence. Clearly HCW's evidence does not meet their own legal thresholds to even force an arrest - and it never will.
So I suppose a convenient patsy isn't a bad description after all, Snr Dr.