Biological explanations of offending behaviour: genetic explanations

+support for the diathesis-stress model of offending

Sarnoff Mednick et al: study of 13,000 Danish adoptees (neither biological nor adoptive parents were convicts)

• 13.5% adoptees had convictions

• 20% adoptees had convictions when biological parent had convictions

• 24.5% adoptees had convictions when both B & A parents had convictions

Shows genetic influence and environmental factors play an important role in offending

-problem with twin studies

Assumption underlying twin studies that environments of MZ & DZ twins are equivalent

Joseph: pointed out that MZ twins are treated more similarly

So differences in concordance rate could reflect environmental difference that distinguish each type of twin

Twin studies lack internal validity

-problems with adoption studies

Stress prior to birth can affect development to foetus

Even if child is adopted early, influence of environment cannot be controlled for

• Adoption studies lack internal validity

• Weakens source of evidence to support genetic explanation of offending behaviour

-genetics explaining offending behaviour is incompatible with way in which our legal system operates

In court of law, offenders are held morally responsible for their actions

Debatable whether individuals genetic make up could be used as a defence in criminal cases