It is legally impossible (in most countries that I know of... though I admit there may be some where it is possible) to consent to any act that will cause harm to you. The only exception is medical consent and that comes under very strict guidelines and rules and you need to be a qualified physician to apply this exemption and have the procedure you plan to do approved and risk assessed by your ethics committee.

Not sure what happened at the end of the German cannibal trial. If he did get away with not being charged with first degree (apart from the fact that we don't have a concept of first degree murder in European courts - we don't differentiate it as much as American courts do, its either murder or manslaughter) then it was probably due to some concept of diminished responsibility. Either there was an appeal of insanity by the defense or the prosecution realised that there was better chance of a conviction if the manslaughter charge was pressed over the murder charge. Either way, I doubt it was due to the concept of consent. If anyone knows more details I would be interested in finding out what happened.

As for the two subs... yes, that is concerning. My main concern is that they are too naive. They are offering more than they may fulfill in real life and that is never good for any BDSM relationship. Major safety concern, especially if they come across someone predatory pretending to be a Dom...