The degree of civilization in a society can be judged by entering its prisons. Fyodor Dostoevsky
No matter how much we agree that putting people in prison is often necessary, we shouldn’t forget that in doing so we limit their human rights. Such limits are not impossible in the system of human rights, but should be kept to a minimum necessary for the protection of other rights or the rights of others. Hence, arbitrary arrest, or arrest for “crimes” which do not violate other people’s rights – such as political “crimes”, speech “crimes” etc. - is unacceptable. Moreover, in those cases in which imprisonment is an acceptable measure in view of the protection of the rights of others, there’s no reason to accept prison conditions that add human rights violations to the human rights limitations already inherent in the fact of incarceration itself.
Inhumane prison conditions are often the result of the general poverty of a country. A poor country will have poor prisons. But poverty doesn’t explain everything, as is shown by the problems in some of the prisons in relatively wealthy countries. Prisoners are often viewed as subhuman, deserving not only imprisonment but imprisonment under any condition. However, such a view is self-defeating: bad prison conditions create subhuman behavior. The ripple effects of bad prison conditions do not stop at the prison walls; they reach every corner of society. Not a lot of imagination is required to see what happens when prisoners leave the hell holes that are used as prisons in some countries. Or better, if they leave. If they leave, it’s often in a coffin, or at best with their mental and physical health destroyed.
More on prison conditions here (on overpopulation in prisons), here (prison conditions in Iran), here (prison rape), here (again on overpopulation), here (solitary confinement), here (juvenile incarceration). Here are some statistics. And here’s an collection of images on prison conditions, past and present:
(source, read the full horror story about this prison ship, used by the British during the American Revolutionary War)
Other collections of human rights images are here.