colins feeling guilt...hmm
dealing with those who are severely mentally ill is very difficult ....and something what may be as innocent as making remarks or decisions that the ill person is not happy with can have effects on them far out of proportion to how a mentally well person would react.
saying what may be perceived as the wrong thing can be all too easy....and from which guilt may form...
the position someone like Colin needs to take is that there was no intention of malice and so there should be no guilt should he form the impression that anything Sheila did was attributed to anything he may have done or said.
the question arises though....if colin felt some guilt....then he must also under the surface believe Sheila did kill the others.