So they claim, but as the Court correctly pointed out, the police had other means to establish who operated the meth lab. More than anything, the police were interested in establishing who resided in the bedroom where the lab was found. Funny thing though, they never tested anything in the bedroom for fingerprints except for the lab equipment and the books. They never interviewed anyone who might have been able to tell them whose bedroom it was. They never collected or analyzed any DNA or other forensic evidence that may have been in the bedroom. Claiming that the book's purchaser was information necessary to establish occupancy of the bedroom is laughable, to say the least.
They also wanted to establish intent to manufacture, which is almost absurd. The lab equipment, the meth, and the "how-to" books at scene--regardless of who purchased them--were more than sufficient to prove intent.
Not until you identify who bought them. Seems you caught yourself up and established my point.