Biological Criminal Behavior: Andrea Yates

Biological Criminal Behavior: Andrea Yates

Postpartum Psychosis

Considerable controversy surrounds genetic or biological dispositions as causes of criminal behavior. Evidence supporting and opposing this view exist which often confuses lay persons who tend to overemphasize biology and genetic factors or oppositely give them no importance. This is a troubling aspect of criminal justice seen in an examination of the Andrea Yates, revealing a tremendous grey area in biological crime theory.

Background of the Andrea Yates' Case

In 2001, Andrea Yates would be charged with capital murder for the drowning deaths of her five children. Her subsequent conviction would be overturned, and Yates would be found not guilty by reason of insanity in 2006. Yates suffered a rare condition known as postpartum psychosis, which caused her psychopathic behavior. The case was tried twice because of the confusing and difficult nature of showing the biological and cognitive factors causing Yates' criminal behavior.

Horrific Crimes & Public Outrage

Complicating the Andrea Yates case is the horrific nature of her crimes. The killing of children draws severe outrage and this taints all parties involved including juries and prosecutors. This is a common issue in the law with horrific crimes and often because law enforcement tends to view crime from a focus on "intent," which often returns guilty verdicts because one can be insane and act deliberately. Because Yates systematically drown each child, she appears have understood her actions, but intention or deliberate action does not mean a person is sane. 

Under the law, Yates could not be held responsible for her actions if proven she did not understand the consequences of her actions (Charles & Bishop, 1987). The Yates defense originally presented an an insanity defense, claiming postpartum depression (PPD) and hormonal imbalances as the cause of Yates' criminal behavior. Yates was found guilty of murder due to the fact that Yates acted in some instances with premeditation or seemed to understand the difference between right and wrong. For instance, Yates readily admitted to waiting for her husband to go to work before killing the children. The case was tried again with the same defense and a separate jury found Yates not guilty by reason of insanity. These two different outcomes show how misunderstood and controversial biological theories of crime are often viewed.

PPD & Issues with Biological Behavior Causes

In the case of Andrea Yates, there was a significant history of mental issues pertaining to pregnancies and evidence of PPD. This history was coupled with the fact that on more than one occasion, doctors had warned the Yates family that Andrea was unstable. PPD as a condition has scientific validity and is considered a viable defense. PPD has been shown to cause states of psychosis and abnormal thinking and behavior. Yates was described by psychiatrist Debra M. Osterman, the Mental Health and Mental Retardation Authority of Harris County, Texas as being so psychotically depressed that the killing of the children seemed the only way to save their souls and that Yates lacked any understanding of the wrongness of the crime (Kunkle, 2014).

Despite there being evidence for genetic and biological causes for criminal behavior such as in the Yates’ case, controversy continues because of the inexact nature of diagnosing these biological theories. For example, the Big Five Personality Theory, posits that personality is composed of a number of broad dispositions including extraversion, agreeableness, conscientiousness, neuroticism, and openness (Boyd and Bee, 2006). It is believed that the interaction of these five traits determines a person’s behavior and personality (Boyd and Bee, 2006).

Theories such as the Big Five are difficult to utilize in criminal cases because these theories only show propensities for certain traits or behaviors. There is considerable argument as to the influence of these traits. It is also difficult to distinguish biological components from environmental ones. For example, there are theories of criminal behavior that claim that hormones can impact behavior. It is possible that extreme behavior can be caused by hormone imbalances but these cases (such as Yates) are extremely rare. There is a lack of consistency in the data due to the fact that most people can control their emotions so the likelihood of extreme behavioral changes is much lower.

One of the most serious issues in biological theories is the fact that there are no common threads that apply to all behavioral issues. For example, in the case of serial killers, there is often many inconsistencies with profiling these individuals which means that their behavior, if genetic, is too broad in dispositions to create a uniform system of diagnosis. One of the most famous serial cases shows this issue with biological theories. The Green River Killer never exhibited any of the biological traits or dispositions for violence would confess to killing forty-eight women across twenty years during which time Ridgeway held regular employment, married, divorced, and attended church appearing to be a normal person (US Department of Justice, 2005).

Another problem with biological theories of crime is that there is no means of identifying the border between biology and environmental causes. More specifically, no one can assess where biology or genetics takes control over the behavior. This problem is likely the result of antiquated thinking concerning nature vs nurture arguments that still persist today.

The Pro-nature and Pro-nurture perspectives are a long standing dichotomy of thinking pertaining to human behavior. The classic argument between these perspectives has centered on what influences and determines human behavior; environment, upbringing, social forces, (nurture), or genetics, chromosomes, and genes that determine traits and characteristics (nature). While both of these perspectives carry merit, they are both independently and dependently flawed when critically examined.

The nature vs nurture arguments rely on the idea that behavioral factors are determined exclusively by one or the other element or that one element such as nature overrides the other element of nurture. This argument is outdated due to the fact that science recognizes the intrinsic link between environment and genetics as well as the inseparability of these elements (Pinel J. P., 2011).

The new scientific view of genetic factors provides increasing evidence for the idea that biological causes are present in criminal behavior, however, this also creates the issue that there is no means of examining the strength of these biological factors or how they impact behavior with regard to environmental forces. The appropriate means of categorizing biology and environmental factors is to separate the contributions of genetics and experience when measuring the development of differences among individuals. This is an extremely subjective measure as no one can point to a specific gene or factor present in individuals and say with certainty that this is a biological cause. For these reasons, cases such as Andrea Yates continue to test the boundaries of science and law and create intense controversy.


Charles, W. T., & Bishop, D. M. (1987). Criminal Law: Understanding Basic Principles. Newbury Park, New York: Sage.

Faith McLellan. December 02, 2006 Mental health and justice: the case of Andrea Yates World Report Volume 368, ISSUE 9551, P1951-1954, December 02, 2006 Published:DOI:

Federal Bureau of Investigation. (1979). John Wayne Gacy Part 01 of 01. Retrieved April 28, 2014, from

Kunkle, F. (2014, September 27). What makes mothers kill their own children? Retrieved from The Washington Post:

Pinel, J. P. (2011). Biopsychology (Vol. 8 ). Princeton, NJ: Allyn & Bacon Pearson Education.

US Department of Justice . (2005). Serial Murder Multi-Disciplinary Perspectives for Investigators. Retrieved April 28, 2014, from Federal Bureau of Investigation:

Article Updated: 12/02/2021


Triola Vincent. Tue, Feb 02, 2021. Biological Criminal Behavior: Andrea Yates Retrieved from

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