First, let’s assume we’re discussing characters who are difficult to classify as either good or evil because they contain strong elements of both. The kind of guy or gal who may be either hero or villain. Most people have a touch of ambiguity in their moral makeup, but the bad guy who’s capable of the occasional kind deed and the hero who messes up now and then aren’t morally ambiguous, they’re just human. The classic example of moral ambiguity is Hamlet. Someone capable of both heroism and perfidy, and hugely conflicted about it
While I’ve never created a Hamlet, I believe there are two morally ambiguous characters in my novel THE BREASTPLATE OF FAITH AND LOVE. Mickey Cullion is an ex-con striving for redemption who nevertheless commits a brutal murder in the heat of passion. His hard work in helping others at a storefront mission is countered by tendencies he hasn’t been able to conquer. We sympathize with Mickey for the good he has done while we recognize the failure of his better nature to prevail at a crucial moment.
As writers, we sometimes hide the moral ambiguity of a character, so that their turn to evil comes as a surprise late in the story. To make this real, the motive for so acting has to be revealed, and it will need to be convincing for the reader.
In BREASTPLATE, Claudia Chitworth is such a character. A grandmotherly type, Claudia is first seen worrying about the welfare of a young boy entrusted to her son’s custody. Her attitude is benign and her concern sincere. But late in the novel we learn that her motive has been deeply selfish, and that she has undermined my PI’s investigation as well as her own son’s good intentions. While not the climactic moment of the novel, the revelation of her perfidy is the key to the denouement.
In a crime novel, especially one in either the noir or the thriller genre, it’s my opinion that the morally ambiguous character will provide both the reader (and the writer) the most profound insights into the human heart of the story.