From a sample of 1,956 adolescent delinquents referred to us by the court for physical, psychological, psychiatric, educational, and social examinations, 71 delinquents convicted of homicide were matched with 71 nonviolent delinquents by age, race, sex, and socioeconomic status (SES). These two groups were compared on the basis of these evaluations by stepwise discriminant analysis, matched pairs, two‐tailed t‐tests, and nonparametric tests. Adolescents who kill have a tetrad of symptoms: (1) criminally violent family members; (2) gang membership; (3) severe educational difficulties; and (4) alcohol abuse.

To study the risks of abuse, violence, and homicide, 5 studies of groups at risk for violence are summarized. 192 Abused Infants, 181 Abused Children, 127 Homicidal Youth, 425 Assaulters, 223 Rapists, and 223 Molesters were randomly selected and tracked in court, probation, medical, and school records, then compared with carefully matched groups of Controls and (in older groups) Nonviolent Delinquents. In adolescence or adulthood, these groups were classified into Later Homicidal (N=234), Later Violent or Nonviolent Delinquent, and Later Nondelinquent subgroups for more detailed comparisons. Shao's bootstrapped logistic regressions were applied to identify risks for commission of homicide. Significant predictors for all homicidal cases in these samples were number of court contacts, poorer executive function, lower social maturity, alcohol abuse, and weapon possession. Predictors for the 373 Abused cases (Infants and Children) were court contacts, injury, burn, poisoning, fetal substance exposure, and parental alcohol abuse. Predictors for the 871 Violent Delinquent cases (Assaulters, Rapists, Molesters) were court contacts, poorer executive function, and lower social maturity. Accuracies of prediction from the regressions ranged from 81% for homicidal sex offenders to 87 to 99% for other homicidal groups.

To identify risks for commission of homicide, 26 convicted Homicidal Youth (M age = 14.9 yr., SD = 1.4; n = 26; 1 girl, 25 boys) were matched with 26 Nonviolent Delinquents and 26 clinic-referred Controls. Youth were tracked backward 8 years (M = 7.7 yr., SD = 15) and forward 3 years (M = 3.1 yr., SD = 1.2) in records. Data analysis was Shao's bootstrapped logistic regression yielding area under the curve (AUC) and odds ratios (OR). Predictors of homicide were poorer executive function (OR = 7.04e+40), violent family (OR = 4.01e-16), and alcohol abuse (OR = 7.33e-17; AUC = .97, 95% CI = .77-.99). From earlier studies, 101 Homicidal Youth and their Controls were reanalyzed similarly. Predictors were poorer executive function (OR = 6.51), lower social maturity (OR = 0.28), weapon possession (OR = 26.10), and gang membership (OR = 4.14; AUC = .98, 95% CI = .96-.99). Groups were combined, i.e., 26 and 101 Homicidal; 127 Homicidal Youth (7 girls, 120 boys) and their matched Controls were tracked in records. The predictor was poorer executive function (OR = 3.34e-21; AUC = .98, 95% CI = .96-.97). When 127 Homicidal Youth were compared with 127 matched Nonviolent Delinquents, predictors were poorer executive function (OR = 2.83e-02), weapon possession (OR = 1.63e-10), lower social maturity (OR = 1.15), and use of special education services (OR = .94; AUC = .94, 95% CI = .37-.99).

Youth development and prevention of violence are two sides of the same public policy issue. A great deal of theoretical and empirical effort has focused on identification of risk factors for delinquency and development of interventions for general risks. Recent calls for changes in public policy are evaluated here--and challenged--in light of new comprehensive, longitudinal empirical data on urban violent delinquency. Treatments such as prenatal care, home visitation, prevention of bullying, prevention of alcohol and/or drug abuse, promotion of alternative thinking, mentoring, life skills training, rewards for graduation and employment, functional family therapy, and multidimensional foster care are effective because they prevent or ameliorate risks for delinquency occurring during development. At present, the best treatments yield 10 to 40% reductions in delinquent recidivism. Better controlled application of developmentally appropriate treatments in higher doses, with narrow targeting of the highest-risk youth based on actuarial testing--rather than less accurate clinical judgment--should result in higher effectiveness. Such a focused approach in a geographical area with high homicide rates should be cost-effective. A prediction of cost-benefit outcomes for a carefully constructed example of a large-scale program is presented.

To assess the risks predicting reoffense, 223 Rapists (M age = 14.2 yr., SD = 1.5; 25 girls, 198 boys) were matched with 223 Nonviolent Delinquents; risks were analyzed using logistic regression. The one predictor was prior court contacts (OR = 1.55e+12; AUC = .99, 95% CI = .98-.99). 223 Molesters were similarly matched with 223 Nonviolent Delinquents; this comparison yielded three predictors: previous court contacts (OR = 4.55e+23), poorer executive function (OR = 2.01), and lower social maturity (OR = .97; AUC = .98, 95% CI = .97-.99). Records for all cases (now M age = 24.2 yr., SD = 1.4) were reviewed forward 10 years and youth were classified into groups: Sexual Homicidal (1%, n = 7), Delinquent Rapists Later Adult Rapists (11%, n = 73), Delinquent Rapists (21%, n = 144), Delinquent Molesters Later Adult Molesters (10%, n = 69), Delinquent Molesters (23%, n = 153), Nonviolent Delinquent Later Nonviolent Adult Criminals (7%, n = 45), and Nonviolent Delinquents (27%, n = 178). Comparison of Sexual Homicidal cases (n = 7) with their matched Controls (n = 7) yielded one predictor, poorer executive function (AUC = .89, 95% CI = .71-.93). When Sexual Homicidal cases were matched with Nonviolent Delinquents, predictors were low social maturity and prior court contacts (AUC = .81, 95% CI = .64-.93).

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To study risks of abuse, violence, and homicide, 181 Abused Children (M age = 12.85 yr., SD = 2.74; 58 girls, 123 boys) were matched with 181 clinic-referred Controls. Data analysis was Shao's bootstrapped logistic regression with area under curve (AUC) and odds ratios (OR). Predictors of abused status were court contacts (OR = 2.04e+22) and poorer executive function (OR = .81; AUC = .99; 95% CI = .97-.99). Groups were tracked forward in records for 9 years (M = 8.78 yr., SD = 1.41). Looking forward, youth (M age = 21.63 yr., SD = 2.07) were classified into Abused Children Later Homicidal (5%, n = 10), Abused Children Later Violent (23%, n = 41), Abused Children Later Delinquent (28%, n = 50), Abused Children Later Nondelinquent (44%, n = 80), and Controls (n = 181). Data were analyzed with two more logistic regressions. Predictors of Abused Children Later Homicidal compared with Controls were number of court contacts (OR = 50,398.78) and poorer executive function (OR = 79.72; AUC = .91; 95% CI = .80-.95). The predictor of Abused Children Later Homicidal contrasted with Abused Children Later Nondelinquent was court contacts (OR = 2,077,089,352; AUC = .87; 95% CI = .65-.95). The common predictor for Abused Children and Abused Children Later Homicidal groups was court contacts.

There have been many attempts to explain violent behavior, identify its causes, and predict its occurrence among youth and adults. Research and theoretical constructions have dealt with such far-ranging aspects as childhood health, peer and parental interactions, neuropsychological function, school and community support, and substance use and dependency. Theories have tended to focus on one or a few of these aspects, but there is an effort by many researchers to converge on an integrated approach. By demonstrating unique risk patterns in random samples of later-homicidal abused infants, children, and youth, violent and homicidal delinquents, and homicidal adults, five studies by Zagar and colleagues provide the best current empirical evidence for a view of the development of delinquency as a process of accumulating risks. These risks begin with prenatal substance exposure and continue with abusive or neglectful parenting, academic failure, court contacts, compromised executive function and resultant poor social functioning. Analysis by sex shows that males' and females' risks are virtually identical. Various theories are evaluated with respect to these empirical risk patterns for development of violence and homicide. A proposal for the necessary elements of a successful, overarching explanatory theory is offered.