Hi Folks, I think it is bad to jump immediately to conclusions. A lot of assumptions may have been made here. I agree with Marilyn, talk to the person. I would like to know the circumstances (overworked, insufficiently trained, etc, etc). Was there a second checker, or was it on-call. If we sacked all techs who had made a mistake in any areas of a lab (before you think it, yes, I know this is different as it is a serious error), the labs would be pretty lonely places. I am more wary of an employee who would tell me they have not made a mistake (or of those who would attempt to cover them up). I also agree with Marilyn, that if this person has sound, logical reasoning, they will have learnt from this mistake and are unlikely to make a similarly serious error in the future. If this is not the case, simple observations of their working habits will soon demonstrate if they do not think in a systematic, logical progression for a given process. Try them on a simple double antibody mixture ident. Who checked the references on hiring? Maybe they were told he/she was agreat worker, but for this single abherrent issue. Lots of privacy issues here to be wary of too. Good Luck. Cheers, Eoin