The minimum age of criminal responsibility is the age from which a child can be held responsible for any of his/her acts infringing penal laws. In other words, it is the age from which they can go to jail if they kill, rape or torture someone, commit some robbery, assaults or any othe rmajor crimes. Below that age, they are seen as innocent by default.
In the USA, the minimum age is 7 years old in most states. However, at the other end of the scale, it is 18 (!) in Belgium.
European countries tend to have higher min. age than English speaking countries. While it is 8 years old in Scotland, and 10 in England and Wales, it is 12 in Canada and the Netherlands, 13 in France and New Zealand, 14 in Italy, Austria, Germany and most of Eastern Europe, 15 in Nordic countries, 16 in Portugal and Spain, and 18 in Belgium and Luxembourg. It is 14 in Japan and China.
In the light of current youth riots in France (many of whom are between 11 and 15), it would be interesting to discuss when should be the minimum age for someone to be held responsible for his/her criminal acts. I think that somehwere between 13 and 15 is old enough.