"Jacob’s Syndrome" – Xyy Genotype

Although the XXY karyotype has been associated with some forms of crime (Stockholm et al., 2012) most studies have focused instead on individuals who have the XYY or “supermale” mutation, in which males have an extra Y chromosome. In turn males will possess 47 chromosomes instead of the normal 46, this can be because of inaccuracies during cell division (Robinson & Jacobs, 1999). Affecting 1 in 1000 new-born males, the XXY genotype is rare and was first reported in 1961, when a male was discovered to carry this gene when he fathered a Down Syndrome child. Following this, there was a surge of reporting amongst males between then years of 1961 and 1965, but only a minute few were actually reported to carry the gene. Conventionally, these males are very tall (over 6 feet), and experience poor coordination, high levels of testosterone, severe facial acne and have a very low IQ, otherwise they appear normal.

In 1966, criminal law was spun into controversy when Richard Speck, who was convicted of murdering eight nurses in Chicago, was also found to possess the extra Y chromosome. However, subsequent appeals were not upheld in a court of law and he was sentenced to death (Horan, 1992). A number of other cases following this showed a similar outcome as although they had the XXY karotype and pleaded insanity, however it was not believed to be admissible in court (Bartholamew & Sunderland, 1966; Saxe, 1970). The feature that tends to be most commonly recognised amongst literature is that individuals with the XXY defect have a ‘low’ intelligence, and have a higher tendency to commit crime. Another feature commonly seen amongst the offenders is that they always predominately tall, however this cannot be used to explain offender behaviour alone.

Thus, combined they can portray a casual link between offender phenotypes (Horan, 1992). This paints a frightening picture, in which males who are of a taller stature and lower intelligence level are stereotypically linked to crime and at a higher risk of imprisonment due to bias by law enforcers, and possibly fear (Hunter, 1966). Jacob’s syndrome has been widely associated with behavioural problems, in turn causing geneticists to assume they will lead to a life of aggression which is not always the case but can be fairly common. Studies show that those who do display behavioural disorders tend to be unstable, have limited concern for their actions, show little emotional response, little empathy and compassion for others and aggressive outburst are commonly seen (Price & Whatmore, 1967). Furthermore, when socioeconomic parameters are taken into consideration it is seen that the characteristics of the XYY karyotypes are much closer to that of the controls (Stockholm et al., 2012). Despite the fact that some studies have argued there is a link between this genotype and aggression, the majority of studies have disproved this with only slight bouts of antisocial behaviour seen in larger populations (Götz, Johnstone & Ratcliffe, 1999). Overall, it can be argued that the majority of population data seen is relatively biased, with individuals who display certain phenotypic characteristics e.g. height and IQ levels being targeted. Many studies also have failed to take into account mental instability unrelated to the karyotype which may affect behaviour outwardly but separately from the gene (Walzer, Gerald & Shah, 1978), and as most criminal cases using XYY karyotype were inadmissible in court, it would seem fair to argue the authenticity behind the evidence.