The human rights issues created by incarceration are evident, I think: locking people up means taking away a number if not most of their liberties, most obviously their freedom of movement, freedom to work and political freedom in some cases, as well as their physical security and privacy. Other rights violations have to do with the kind of people who are locked up and the often substandard conditions in which many prisoners are kept, even in rich countries such as the U.S.:

Some people clearly deserve to be put in jail, and often that is what is required and necessary in order to protect the human rights of their (possible) victims. There’s also a deterrent effect: one study has shown that a 10 percent increase in incarceration is associated with two to four percent drop in crime. In the U.S at least, there’s a correlation between soaring incarceration rates (see below) and spectacular drops in crime rates. However, other data point to little or no effect of mass incarceration on crime: