> Hang on, just to clarify: if someone else puts a file on my PC without my knowledge, without me ever having seen or opened it, he could call the police on me,

> Hang on, just to clarify: if someone else puts a file on my PC without my knowledge, without me ever having seen or opened it, he could call the police on me, and it would get me convicted? Yes. In such a case, a presumption of innocence would be true in theory but of no value at all in practice. Such an attack could even be carried out remotely -- an attacker could compromise a machine remotely, then plant incriminating evidence on the compromised machine (i.e. child porn, terrorist literature, drug-dealing evidence, etc.), then alert the authorities. This plausible scenario is another reason to vigorously protect one's computer against external attacks.