Several expert witnesses have testified in the trial of Alvaro Castillo about the hereditary nature of certain mental disorders. The issue of genetics usually comes into criminal trials through DNA, not through the defendant’s family tree. And it seems to me (a non-lawyer, non-psychiatrist, and non-geneticist) that using genetics in law is a very slippery slope. I would like everyone to take a step back and think about this.

Your DNA Makes You Who You Are – Or Does It?

Years ago – and perhaps still – we worried whether it was “nature or nurture” that makes us who we are. We have since learned enough about genetics to have decided that both factors significantly influence personality development. I don’t think anyone now believes that even identical twins (who have identical genes) have identical personalities. (Numerous twin studies, such as the Minnesota Twin Family Study have been conducted over the past 30 years, including twins separated at birth; while they often have eerily similar personalities, they are not identical.)

Then there’s the saying that “you are what you eat.” I take this as a way of explaining that what you consume shapes your body, hurts or helps your growth, and often affects your mood.

However, geneticists are now discovering that what you consume can even alter your DNA.

I’m not talking about chromosome damage from consuming carcinogens, although that certainly falls in the class of DNA-alteration-by-food. I’m talking about a diet that alters the genes you pass on to your children.

In the Feb. 1, 2009 issue of GEN magazine, Dr. Richard Stein reports on “epigenomics” studies at Duke University, conducted by Dr. Randy L. Jirtle:

• “It is increasingly evident that genetics alone cannot explain the complexity of phenotypic characteristics” [  ] . . . . Two inbred mice, despite being genetically identical and having the same sex and age, were found to be phenotypically distinct. While the mother of one of the mice received a normal diet, the other mother’s diet was supplemented with methyl donors . . . .”

“Phenotypes,” as I understand the concept, are an organism’s physical characteristics. While it was previously known the environment can damage or change an organism’s physical characteristics, it was not known that the changes could be passed on to progeny.

In Dr. Jirtle’s experiment, a fat, yellow mouse gave birth to a small, gray mouse, without mating with a small gray mouse.

Unfortunately, what is true in lab rats is also true in human beings.

• Sidebar: Of course, if the premise is correct, lab rats and people could consume things that modify their phenotypes in a good way. And I certainly don’t want to disparage small, gray mice any more than I would small, gray-haired people (especially since I am on the verge of becoming just such a creature). Miss Marple comes to mind.

Not only one’s hair color, but one’s brain, can be altered by the environment (nurture, so to speak) and that alteration can be passed on to offspring.

No DNA Marker for “Psycho Killer”

My point here is that it may not be relevant or appropriate to present a detailed, multigenerational family tree in a criminal trial (as did social worker Deborah Grey in the Castillo trial).

• Sidebar: If I have identified the same Deborah Grey on LinkedIn, her master’s degree is in Theater. Can this be true? (Maybe she isn’t really a forensic social worker, but she just plays one on TV.) My apologies to everyone on LinkedIn named Deborah Grey for misidentifying you.

Family trees are irrelevant to any individual’s specific behaviors. A family tree does not prove that a person has a predisposition to an illness, even in traditional Mendelian genetics. Science cannot yet explain every “allele” in a person’s DNA – and certainly not a marker for schizophrenia. And now science is discovering that environmental factors (including substances consumed) can modify one’s genetic makeup.

Given the assaults to one’s body that the environment presents the only significant generation for the purpose of assessing a tendency to mental illness in one’s genome is the previous generation. Even your siblings and your parents’ siblings are completely irrelevant. Furthermore, a parent’s schizophrenic episodes could have been induced by an environmental factor (such as drug abuse) and do not necessarily impact his child’s DNA.

• In other words, because your mother’s family has a history of mental illness, it does not mean that you inherited your craziness from her. And because your mother’s sibling had a history of mental illness it does not mean that her panic attacks are genetically based. (I would have panic attacks, too, if I had a husband like Mrs. Castillo had.)

I’m not a geneticist, but I do understand that in many ways DNA is poorly understood even by scientists. No one can yet point to a specific “genetic marker” for mental disorders. When physicians say that “a predisposition” to such a disease is hereditary, in fact they are relying on genealogies, not the genome, for their conclusions.

• Sidebar: Psychiatrists are not psychologists. They are physicians who specialize in brain problems that can be treated with drugs. Physicians are not geneticists; they are clinicians, not theoreticians. To formulate a theory you must have a Ph.D.

The Slippery Slope Is Also The Primrose Path to Hell

Imagine what would happen if a geneticist were arrested and tried for murder, who then used the insanity defense, knowing his family on both sides had an extensive history of  schizophrenia. Or what if the cops went after citizens based on their families’ history of mental illness?

• In fact something similar did happen in England, an investigation of a rape/murder led to the first use of DNA in criminal forensics. Joseph Wambaugh’s The Blooding is true-crime reporting of that case. The “bobbies” took DNA blood samples from every male in town to compare to the crime scene samples.

Using a person’s genetic history against him or her in a criminal trial seems as unfair to me as using those “excited utterances” and other hearsay evidence.

• Sidebar: I’ve written before about the logical flaws in using hearsay of the defendant’s words as evidence. For now, I will simply point out how hearsay of Alvaro Castillo’s words has been used against him in his trial: The defendant’s mother testified about what he said to her right after the “incident.” She claimed he asked for forgiveness. This is only hearsay. She may not be credible. She was a defense witness, but it is the prosecution that seems to have made the best use of her testimony. If Castillo is found guilty because of this, I think it should not only be grounds for an appeal, I hope Judge Michael Morgan declares a mistrial.

I can imagine a case like that of Alvaro Castillo’s in which the prosecution could use his genetic history to rebut the insanity defense. What if the prosecution brings on another social worker with another chart, but one which shows a history of sanity in the family?

I’m also concerned that soon lawmakers could easily, foolishly, and in complete ignorance of science rewrite the law. They might even declare that in order to use the insanity defense, a defendant must first prove a genetic predisposition to mental illness. Or the law might be rewritten to eliminate from the insanity defense mental illnesses defined in the DSM-IV as mental “disorders.” After all, the “science” of psychology does not even use the word ‘insanity.’

What Is the Insanity Defense? When Will the Law Be Sanitized?

A lawyer with an excellent command of the English language needs to bring some sanity to the insanity defense.

I suspect the issue needs to be addressed by the U.S. Supreme Court. After all, when a defendant’s right to life is at stake, it seems grossly unfair for state laws regarding the insanity defense to be at variance.

As far as I can determine (and I am not a lawyer) each state adheres to a different standard for the insanity defense, as the Cornell University Law School website explains: “The insanity Defense and Diminished Capacity.” Not only have state legislatures written widely varying statutes governing the application of the insanity defense, each state’s Supreme Court has also written different pattern jury instructions about the insanity defense. (Those are the instructions judges read aloud to jurors.)

“The McNaughton Rule” seems to be the most popular of these standards. Unfortunately, it was formulated in England, not America, in 1843. That’s correct folks. Over 150 years ago, long before anyone had ever heard of Sigmund Freud, let alone “psychosis.”

No wonder the jury in the Castillo trial will be pulling out their hair by the time they reach a verdict.