RELATIONSHIP BETWEEN THE OFFENDING FREQUENCY (λ) OF IMPRISONED AND FREE OFFENDERS*

In the public debate over incarceration policy, there is considerable disagreement about what value of individual offending frequency (λ) is appropriate to use in estimating incapacitative effects. This article provides an approach for estimating the mean values of λ for diverse subsets of the total offender population, with particular emphasis on subsets generated by filtering through various stages of the criminal justice system. Sharp differences in offending frequency are displayed between robbery and burglary inmates, across three states, and particularly between resident inmates and free, active offenders. Free offenders average 1 to 3 robberies and 2 to 4 burglaries per year, while resident inmates have λ values 10 to 50 times higher. Differences result from the underlying levels of criminal activity and the sanction Levels that offenders face. A highly heterogeneous distribution of offending frequency in the total population of offenders combines with relatively Low imprisonment levels to lead to substantial selectivity of high-λ offenders among resident inmates and a correspondingly low mean value of λ among those offenders who remain free. These results have important implications for estimating incapacitative effects of an increase in incarceration, since the additional inmates will be drawn from free offenders whose mean λ is at least an order of magnitude Lower than that of the current inmate population.     

A modification of the microplate method for reverse ABO typing of bloodstains and additional validation studies

The results of additional validation studies of a sensitive microplate hemagglutination assay for ABO reverse grouping of bloodstains are presented. The results of the validation study demonstrate the reliability of the microplate assay for use in routine serological casework. Based on these studies, the microplate assay has now replaced the Lattes crust test for ABO reverse grouping of bloodstains in the FBI Laboratory.     

RATE OF OFFENDING IN JUVENILE CAREERS: FINDINGS OF CONSTANCY AND CHANGE IN LAMBDA *

This study examines changes in the rate of offending in a sample of 8,834 males whose official juvenile law-violating careers included 26,650 offense episodes between ages 8 and 17 The rate of offending of active offenders (i.e., lambda) varied substantially as a function of age, increasing monotonically with age. Lambda, however, was not related to the age at first offense. In fact, the average lambda was amazingly constant at each individual age level regardless of the age at which offending began or desisted. Results are discussed in the light of age-crime curves known from other data sets and from the perspective of developmental changes in the rate of offending as youths grow older.