Sorry to be not as intelligent as I could be on this topic, but if you're considering Miss Climpson and her conscience, you have to include her breaking a sworn oath (one of the other things I find as sloppy in DLS in her approach to legal matters, actually) to tell Lord Peter the secrets of the jury room in Strong Poison.

I actually can't believe in her doing so - still less doing so without any overt strife with her conscience as in Unnatural Death - but do it she does. So in the words of the Miserere, her acts in Strong Poison are from the beginning "shapen in sin".