I'm guessing this could - as someone pointed out - be done when the SL hit takes, without a huge upheaval of any code. Just put a call in the SL drop method which sends an email. This would mean getting numerous mails per kill though - one from each person - but I imagine would be the easiest way to do this.
So, say, Santos takes a SL hit for killing Illyria, that triggers the "I'm guilty" mail. As well as anyone else who took a SL hit for that kill.
I appreciate that this would result in MORE mails as someone said, but I guess this would be the easiest way to implement this - without knowing anything about the way NC's coded, so it may be a load of bull.