Predicting which children will go on to commit crime is fraught with difficulties - and early intervention to prevent it may even damage and criminalise children.
These are findings in major University of Edinburgh research at a time when Scotland's policymakers are ever more committed to pre-empting social problems in early childhood.
A report based on the Edinburgh Study of Youth Transitions and Crime that tracks 4,300 youngsters who started secondary school in 1998, finds "a sharp distinction between those who were identified at an early age as being `at risk' and those who later became offenders".
One statistic in particular showed how difficult it is to identify future offenders, even by their mid-teens: 76 per cent of violent offenders at 17 had not been referred to either social work or the children's hearing system by the age of 15.
Early intervention with at-risk children "seems to do little to stem involvement in offending" - and may even stigmatise and harm them.
For many children, early intervention results in "repeated recycling and labelling" which "places serious limitations on the capacity of the youth justice system to reduce crime because it may be damaging to young people in the longer term".
Scotland's welfare-based system is not in itself damaging to children; it is rather "the cumulative effect of systemic contact over many years which stigmatises and criminalises".
The researchers point to ages 13-15 as the fork in the road which determines whether many children become mired in criminality.
They compared two groups of youngsters: those who were convicted at a young age but later stopped; and those convicted at a young age who continued offending.
There were no significant differences between them at 12. But the 13-15 period was "a significant turning point", when those who would continue offending were more likely to truant, be excluded from school and receive warnings from police.
The 13-15 stage was also pivotal for those first convicted in their late teens or early twenties. In their early teens, "various aspects of their lives deteriorated significantly", including a threefold increase in alcohol consumption.
"Pathways of criminal conviction are associated with changes that occur at critical points in the early teenage years," the research said.
The study establishes strong links between violence and the troubled backgrounds of perpetrators: "Violence is symptomatic of a broad range of vulnerability among both boys and girls," it found.
Violence, like self-harming, can be a coping mechanism for these youngsters amid difficult relationships with peers, family and other adults.
The researchers stressed that children in conflict with the law must not be dealt with purely by the criminal justice system - "you can't deal with their deeds in isolation of their wider needs".
Earlier this year justice secretary Kenny MacAskill, in praising lead researchers Lesley McAra and Susan McVie, said: "The more we resort to formal measures in dealing with children, the greater the risk we draw them further into the system. So we need to use those measures very carefully, and in a way that tackles the needs, not merely the deeds, of all young people who offend."
Knife crime cut
Strathclyde Police figures have shown a dramatic drop in knife crime among under-16s. The number caught with a knife fell 75 per cent between 2006 and 2012.
The Glasgow-based Violence Reduction Unit, led by senior policeman John Carnochan, has won international praise for tackling crime through preventative measures. It has previously argued that funding should be diverted to nurseries if Scotland's violence problem is to be solved.