Mandatory sentences are completely illogical - the idea that law makers should have a hand in determining how judgments should be given - rather than a rubric for how the law and sentencing should be set up - is absurd. We have judges for a reason, and they have the experience to know how long sentences should be.
U.S. prison sentences should be shortened, but this should only occur after certain measures have been met. It's common practice that with good behavior, a sentence can be shortened or special privileges could be awarded. The same practices should be applied when questioning the length of a prison sentence. The inmate should be able to exhibit desirable qualities sincerely in order to be awarded a shorter sentence.
I don't think we need to shorten prison sentences so much as radically change what we're sending people to prison for. Most people who are behind bars these days find themselves there due to something involving drugs. The solution, of course, is to decriminalize many drugs. That way, we can maintain long and harsh prison sentences for those violent offenders who truly deserve them.
No, U.S. prison sentences should not be shortened, because when a person is in prison, they cannot commit any more crimes. It is hard to go to prison. First, a person has to exhaust all tolerance with the local jail system. In order for a person to go to prison they have to have done something really bad, or offended many times. Leaving them in prison keeps them from getting out to commit even more crime.
The prison sentences are fine the way they are. They are given long sentences because they did something bad or terrible and the US wants to see them off the streets and away from people they can harm. They let them out once they are sure these people can be trusted again.
Some sentences are too strict (marijuana possession, for example) but we can't just go across the board and say all prison sentences should be shortened. Some people belong there and are past a point that any good is going to come of them being back on the outside, they earned their terms.
Prison sentences in the United States should not be shortened unless the prisoner is found to be innocent at a later date. People do not go to prison simply for a speeding ticket or jaywalking. People in prison have committed a crime and a serious one at that. The victims of the crime deserve some sense of justice.