When a person is convicted and sentenced to jail, it does not necessarily mean that he or she will stay there for the duration of his jail term. The convict still has other options such as appeal his case to a higher court or have his case modified.
For modification purposes, the Federal government has certain rules but they vary from one state to another. This particular rule allows a case to be corrected or reduced in certain circumstances. Firstly, when an error has been found in the sentence imposed. Secondly, if the defendant serving jail term is helping in another criminal case. A sentence may also be lowered based on a person’s age.
It is possible to correct errors made on your case, regardless of its nature. As long as there are math, technical or other clear errors spotted, the defendant can still appeal his or her case. An example would be the number of years imposed for a jail term.