In Sunday's New York Times Mosi Secret writes an in depth front page article about juvenile crime examining issues concerning the age threshold for prosecuting juveniles as adults: 16, 17 or 18 depending on the state. The article looks at costs and national legislative trends for these prosecutions.
Thirty-seven states, the District of Columbia and the federal government have already set the age of adult criminal responsibility at 18. Eleven states have set the age at 17. New York and North Carolina are the only two states that set the age at 16.
In 2008, the year of the most recent national estimate from the Justice Department, law enforcement agencies made about 2.1 million arrests of teenagers younger than 18, and most of those cases involved 16- and 17-year-olds. The data also showed a drastic decrease in arrest levels since the mid-1990s: there were an estimated 2.9 million such arrests in 1996, when the population of those under 18 was smaller than it is today. (nyt link)
The age for adult responsibility in Tennessee is 18 but transfers to adult court for serious violent crime and persistent offenders can come at an earlier age. It is unusual to see transfers for juveniles offenders younger than 15 years of age to adult court.