A judge has given the "last resort'' sentence of detention to a juvenile with a history of violent armed robberies, including two involving use of knives to hold up rideshare drivers. Queensland Children's Court president Judge Deborah Richards said only two months before robbing an Uber driver, the boy, now 16, was sentenced to two years' probation for violent robberies. When Judge Richards asked him what had happened in those two months, he said: "Dumb stuff''. "It's not. It's violent, dangerous criminal stuff,'' Judge Richards said, telling the teen his offending had an awful effect on not only the victims, but on his mother and siblings.