In this case the judge wasn't constrained by the system and he still agrees with his 12 year sentence. Where the constraint often comes in is the federal minimum sentencing guidelines as pointed out by Shon here[1].
In the 1990s, Congress passed several get-tough-on-crime mandatory minimum sentencing bills. One of those laws requires a judge to impose an additional 25-year sentence for anyone convicted of a second or subsequent firearm charge. Without these laws, Adam may have received the same 12-year sentence I did. Instead, mandatory minimums allowed prosecutors to transform a crime that averages a 10-year sentence into life imprisonment.
In the 1990s, Congress passed several get-tough-on-crime mandatory minimum sentencing bills. One of those laws requires a judge to impose an additional 25-year sentence for anyone convicted of a second or subsequent firearm charge. Without these laws, Adam may have received the same 12-year sentence I did. Instead, mandatory minimums allowed prosecutors to transform a crime that averages a 10-year sentence into life imprisonment.
[1] http://www.theatlantic.com/national/archive/2012/12/i-got-a-...