Overcrowding means two, four, ten times as many prisoners in a room as there should be. In these environments it is no surprise that disease raises its head and that violence erupts. The vast majority of people who are in prison are young men. Not only do they make no contribution to society while they are in prison, there is a real danger that they will continue to be a drain on society after they are released. There is a great deal of research which indicates the limited contribution which prison has little to offer society in terms of crime prevention.
Much crime goes undetected.
Only a very small proportion of offenders in any society ends up in prison. Of those who do, many will commit further crime within a short while of being released. The victims of crime gain little satisfaction from this state of affairs. The adversarial nature of much of the criminal justice process leaves them feeling marginalised and frustrated that their needs are not taken into account. In some societies imprisonment has become big business.