Do you think Mr. Harvey is a developing character?
The term character development can be used in two senses, and one sense is sometimes used interchangeably with characterization. In the first sense, character development refers to the facts and information revealed about a character in various parts of the narrative, or over the course of the story, in order to make clear the character's inner and psychological traits and qualities, beliefs, values, motivations, and intentions (intent). [This sense is sometimes used interchangeably with the term characterization.] These revelations may all be consistent with each other. In other words, what the character thinks, believes, wants, understands, etc. may be the same at the end of the story as they are at the beginning. On the other hand, what a character wants, believes, etc. may undergo an alteration, or change, through the course of the narrative. This leads to the second sense in which character development is used.
In this second sense, character development is used to indicated the alterations, or changes, a character undergoes throughout the course of a story in response to other characters and events over time as time is represented by the story in the narrative. In other words, this sense of character development refers to the way or ways in which a character comes to believe or want different things as a result of a revelation or epiphany; to understand something different about life, the world, themselves or other people; to develop different psychological dynamics, motives, or intents; etc.
In the first sense of the term, Mr Harvey does have character develop throughout the course of the story because new traits are revealed over time, for example, after Lindsey breaks in to his house and when he decides to end Lindsey's life. In the second sense of the term, Mr. Harvey does not have character development throughout the course of the story because his psychological dynamics, his motives, his beliefs, his desires, his intents remain the same (though details may vary, e.g., Lindsey instead of Susie; retaliation murder instead of otherwise; etc.) from the beginning of the story throughout to the end of the story.