In 1961, a condition of an extra copy of the Y chromosome was discovered in males. Now, more commonly known as XYY syndrome or Jacobs syndrome, the disorder causes 1 in 1,000 males to have two Y chromosomes instead of one and 47 overall chromosomes rather than 46.
The only physical symptom of the disorder is increased growth or possible weaker muscle tone, males with XYY syndrome tend to be taller than the average male and experience extreme growth spurts particularly during their pubescent years. The psychological symptoms that correlate to crime are attention difficulties, emotional or behavioral issues and delayed or difficult speech. My theory is that these symptoms do not directly cause deviant behavior, but the frustration they cause does.
In today’s society, there are set roles that genders must conform to. Males must be strong and protective, whereas females should stay home and rely on the male. Even though these gender roles are absurd, there is immense pressure people feel from them. When males are only ever portrayed as strong and protective, a male suffering from weak muscle tone due to XYY syndrome may feel compelled to prove himself. In which they do so through murder or rape; as they perceive violent crime as a show of strength and masculinity.
American forensic psychologist, Dr. Helen Morrison, believes that the abnormality of a possible extra chromosome in killers is revealed during puberty. American serial Killer Bobby Joe Long has an extra X chromosome, this causes excess estrogen to be produced in the male body. During adolescence, he began to grow breasts, thus experiencing anger and embarrassment towards himself. This obviously counteracted the stereotypical male characteristics, causing Long a lot of frustration. He then put all his anger into raping 50 women in a 30 year time frame, then spiraling to killing 10 women within 10 weeks.
Famous serial killer Richard Speck brutally murdered 8 student nurses in Chicago, defendants argued Specks violence was caused by an extra Y chromosome, however the court ruled that the now known XYY syndrome was not the cause of his deviant behavior. Specks suffering of XYY syndrome was later debunked, as researchers argued sampling errors occurred and produced a false chromosome pattern.
A 2012 study into criminality in males with XYY syndrome proved that males suffering from this disorder are more likely to be convicted of violent crime, in comparison to males with the common XY chromosomes. Although many studies show there is a correlation between the XYY disorder and violent crime, we are still uncertain on whether it truly is producing killers and rapists.
My concluding theory is that XYY syndrome does certainly correlate to crime however, it is not the direct cause of the increase in violent behavior. It is the symptoms of the disorder– learning difficulties, speech impediments and emotional or behavioral issues– that are ultimately what cause the XYY male to lash out and be violent. The direct symptoms can frustrate and anger the male to the point of extreme violence.