The daisy drawing is quite interesting IMO. Given the tone of the letter and his rant against the Prosecution, initial thoughts are that it's perhaps aimed at them. i.e. that they have plucked at the clues and have 'landed' on him being guilty based on poor deductive efforts. Although this then doesn't entirely fit with what the narrative of what he says about them. His continual claim is that there is a concerted effort to "fit him up", so I don't know if the daisy plucking drawing is an appropriate analogy in that respect.
A second option is that the daisy picking represents the watching media & public who are trying to decide whether he is guilty or not. He makes a comment in the letter of being "told a long time ago" that the MM case was going to be dropped and he then says "I wasn't telling you because I'm afraid that you and the other English people are going to lose their interest in me and my case, for that reason I beg your silence." Well, the request for silence clearly didn't pan out but it seems his wish for the public interest to continue certainly has. Whether or not CB is guilty, it feels like he is revelling in all this media attention and sees it as one big game.
It reminds me of the comment he made in another letter when Jutta Rabe had asked him whether he was involved in MM's disappearance. He replied "What do you think? Am I innocent or did I commit the perfect crime?". I think he gets enjoyment out of keeping everyone guessing. JMO.
