In order to conceal the murderers true identity, Christie uses Dr. Sheppard to develop a trustworthy relationship with the reader. How does she do this?

Throughout the novel, Dr. Sheppard gives us the appearance of being a relatively neutral narrator. He shares conversations in detail and recounts events with precision. His opinions are limited to the personalities of others, and in what we believe to be his complete honesty. Thus, when he finally explains his actions, we see him as he really is.....smug and without remorse.