What do Twin Studies Tell us about Who gets Arrested and Why?
We know genetics can solve crimes. For over thirty years, DNA evidence has been used at trial both to convict and to exonerate defendants. Blood, semen, hair: all of these can tell us who may have been at a crime scene.
Might genetics be used in another way to solve crimes though? Could a person’s DNA tell us just how likely they are to commit a crime? Twin studies may hold the answers. Those answers, though, are by no means simple.
What are Twin Studies?
Twin studies can be especially useful for determining if human behaviors are the result of environment or genetics. Such studies rely on the fact that there are two distinct kinds of twins. Monozygotic (MZ) twins are genetically identical. Dizygotic (DZ), or fraternal, twins are not.
When twins—MZ or DZ—share the same behavioral characteristic—say, an aptitude for math—that characteristic could theoretically be caused by either genetics or environment. However, because MZ twins have identical DNA, when more MZ twins share a common trait than DZ twins, most geneticists assume that trait must be the result of genetics.
When it comes to a propensity for criminality, several twin studies have found that it’s more common for MZ twins to share this characteristic than DZ twins. This would seem to suggest that an urge to commit crimes may be encoded in our DNA.
Scientists have discovered two genes they think may be responsible for most criminal behaviors. One of these is the MAOA gene. Someone with this gene has trouble regulating the brain chemicals dopamine and serotonin, both involved in aggressive behaviors in humans. Another gene, CDH13, is linked to drug addiction and alcoholism, both of which can be important contributing factors in criminal activity.
Where do We Go from Here?
Such research raises important questions about the criminal justice system. On the one hand, might genetics serve as a reasonable defense for crime? That is, should you be held accountable for robbing a bank if your genes made you do it? A number of court cases have already begun to put this hypothesis to the test. On the other hand, might we reduce crime by simply locking away anyone with the MAOA gene?
While the findings of twin studies offer tantalizing clues to why we behave as we do, they don’t provide the kinds of black and white answers we can apply in a court of law.
In particular, while a trait may predispose someone to a specific behavior, it may be that only the environment can trigger that behavior to come to the surface. We can find useful analogies in other conditions. For example, while some of us may inherit a genetic predisposition to heart disease from our parents, we may never actually develop heart disease unless we have other risk factors like smoking or poor diet.
For now, we can’t blame DNA for criminal behavior; we can only consider it a single factor among many.
To find out more about twin studies or genetics and their relationship to the law, or to get help with your own case, contact Razamuch & Associates, P.C. by phone at (317) 449-8657. Or contact us online or via email at [email protected].