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This blog was featured on 08/16/2019
The Psychology Behind Writing a Murder Mystery
Written by
She Writes
July 2019
Written by
She Writes
July 2019

This guest post was written by J.L. Doucette, author of On a Quiet Street

There’s Always a Reason

I love the board game Clue and trying to find the killer among the six characters, six weapons and nine rooms. The only thing missing is the motivation for the murder. While it’s true that the mystery genre is known for intricate plotting, the mystery novels that I find most compelling contain a psychological motivation for the crime. The motivation for murder is at the core of the story.

I’m a psychologist who writes murder mysteries. My education and clinical training are a perfect preparation for writing mysteries.     

Some things are true in both disciplines. An idea that is accepted in psychology, whether you subscribe to behavioral or psychodynamic understanding of human behavior, is that there is always a reason for any actions humans take.


When trying to understand how a person functions in the world, the psychologist begins by looking at the early childhood experiences, the relationships that formed the interpersonal world of the developing individual. The caretakers who are present in our early world teach us about who we are and how we fit into the world.

The same is true in a murder mystery. There is always a reason for the crime of murder and understanding the back story can make senseless violence a little less terrifying.

Even seemingly random acts of violence stem from causes that may not be immediately apparent but are nonetheless operating to bring the killer to the moment in time when he takes the life of another.

This is not what we usually hear on the news when a murder is reported..Shocked neighbors typically describe the killer as a quiet loner who kept to himself and never caused any problems.

They want to understand. They want to know what kind of person could commit that kind of crime.

The story slowly emerges as facts are gathered and a narrative of the killer’s life is told. It’s never a good story and it begins to make sense how the person described as almost invisible could reach the horrendous moment in the spotlight.

There’s always a reason---it’s true in life and it should be true in fiction.


Murder is often called a crime of passion. It sounds exotic and tragic. It also makes the killer more human. We’ve all felt passion. We can relate.

When creating a credible murderer the most important thing is to establish motivation that arises from the killer’s personality as it was formed by his life experience. Providing the details and relationship dynamics of the character’s early life will result in an interesting and credible killer.

You can write a psychologically credible murder mystery without having a psychology degree. Motivation for all behavior comes from internal reactions to external reality.


When creating a character who kills, I think about many of the same factors found in a psychological report. I consider where the character was born and into what social and economic class, ethnic and cultural identification and religious beliefs. The quality of the parents’ relationship, the number of siblings, how conflict was managed, addictions and family mental health history. Each of these factors contributes to a person’s identity, whether real or fictional.

These are the basic identifying details, most of which never make it into the story. They provide the framework to develop the internal world of the individual. Psychological motivation goes deeper than the surface reason for the crime.

The real story of why this specific person committed murder at this specific time and circumstance is what makes the mystery compelling and takes it to a deeper level.

Who broke her heart? Who told her she was bad? Who made him feel worthless? Who made him feel the world owed him everything? These are some of the questions that can reveal the hidden programming and secret needs of the character who is capable of killing.

If you want your character to be a credible killer, give him a bad childhood. John Garabino, a psychologist who studied incarcerated murderers, found that they scored high on Adverse Childhood Experiences which include physical abuse, emotional abuse, sexual abuse, physical neglect, emotional neglect, household with mentally ill person, household with drug or alcohol abuse, exposure to domestic violence, parental separation or divorce, incarcerated family member.

Character and personality within human relationships. How we are seen and treated by others, the ideas that others have about us, whether we are loved and cared for or rejected and neglected---these experiences contribute to our beliefs about ourselves. Our behavior is a manifestation of what we believe to be true about ourselves.


Gender matters when it comes to murder. Only one out of ten murders in committed by a woman. The reasons that move each sex to take the life of another are rooted in primal, gender-driven needs--dominance for men and survival for women.

Men kill for revenge, in response to jealousy or threat, or because of failure to fulfill the masculine role of providing for their families. Often these murders are preceded by other aggressive and impulsive acts.

Women kill when their security is threatened, to secure resources such as insurance payouts, the changing of a will or to control an environment which has become intolerable such as a betrayal in love or domestic abuse. Men are more likely to kill non-intimates while women kill those closest to them.

 A murder mystery has two characters central to the story---a killer and the person killed. Murder is an event between two people. Readers need to feel for the victim, possibly identify with the victim and so just as much thought needs to go into the development of the victim’s story.

Not only does this make for a more interesting story, but it gives readers what they are seeking when reading murder mysteries---knowing the dark heart of the killer. The place where the internal worlds of the murdered and the victim meet is where the mystery is solved.

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  • Gary Dorion

    Insightful. As a former career court news reporter who covered about 500 murder trials over ten years, I have to say what many lawyers like to tell juries - "it has the ring of truth."

  • Hyba Revising

    What a rich article! It has so many great points, and I find myself thinking about all of the characters in my psychological mystery and seeing how their motives work! I really like delving into the 'why' of the crime and really giving readers a look into the perpetrator's thinking, so this article is right up my alley. Thank you so much for sharing.