I read that as him saying "I can not declare him guilty but my not declaring him guilty doesn't mean he is innocent".
Add one word and it would more accurately reflect what the judge said -> "I can not declare him guilty but my not declaring him guilty doesn't NECESSARILY mean he is innocent".
In other words, there is no way of knowing for certain because the complainants words taken as a whole are unreliable, and as a result "it is impossible to determine, with any acceptable degree of certainty or comfort, what is true and what is false."