Sad story, without an easily defined person to blame.
http://en.wikipedia.org/wiki/Incarceration_in_the_United_Sta... Starting in the 1980's, we began to wage a war on drugs (when used by minorities), and decimated our inner cities. At the same time, we built lots of private prisons, and allowed these companies to write legislation that led to longer prison terms. http://en.wikipedia.org/wiki/File:U.S._incarceration_rates_1... Instead of using data or evidence to develop our penal system, we rely on fear and racist-based emotional politics, fueled by the private prison industry. Locking up kids can make a lot of money. States pay anywhere from $25k to $50k per prisoner per year. It's a cash cow. http://en.wikipedia.org/wiki/File:US_criminal_justice_cost_t... Sometimes, you can even get cash up front for putting kids away in the US!
It happened near me in Michigan in a pretty famous case. An 13 year old was charged with 2nd degree murder that he committed when he was 11: http://www.wsws.org/articles/2000/jan2000/abra-j14.shtml It's getting better slowly, but it was brought on by a bunch of idiots thinking they were 'getting tough on crime' that started in the 80's. A lot of states started passing mandatory sentencing, and started dropping age limits for sentencing: http://www.csmonitor.com/Commentary/Editorial-Board-Blog/201... Pretty shameful stuff.