lyserge
polyfather anomalous
For legal questions like this it very much depends on your country. I only know about US laws but here's what I know...there was a US court case in California a few months ago in which a man had killed bicyclist with his car and admitted doing so on his online web-page. The court ruled that the online admission could not be used as evidence. There was also a case a few years back in which a man was e-mailing death threats against the US president (at that time it was GW Bush) from a public library. Federal agents were actually sent to the public library and physically monitored the place until the man came and typed a further death threat, at which point they moved in and arrested him. It would be very tricky and basically pointless for such an online admission to be used as evidence - authorities would still need a "corpus delicti" - physical evidence - to establish guilt. (I have been unable to find via a quick google search links for these specific cases, just from memory).