A prison is a type of institution which exhibits aggression within groups.
This sort of aggression can be explained through the importation model suggested by Irwin and Cressey who proposed that inmates import their own social histories and violent characteristics which influences their behaviour in prison.
In addition, Marcell et al commented on how pre-prison gang membership is an important determiner of prison misconduct. In prison institutions, gang members disproportionately engage in acts of prison violence as opposed to non-members; research found that gang members in the US were 10 times more likely to murder and 3 times more likely to assault than those outside a gang from a similar age and background.