Murder and Serious Sexual Assault - Lancaster EPrints - Lancaster ...

APPENDIX C
career of offences appearing in the table above will raise (or lower) the risk of future
SSA relative to this individual. A second example is given below:
Example B. A 22-year-old active male offender with prior convictions, at
separate sentencing occasions, for unlawful sexual intercourse with a girl
under 16, shoplifting and stealing in a dwelling. This last offence resulted in a
custodial sentence of three months.
The relevant features are identified from the criminal history. An offence of
unlawful sexual intercourse with a girl under 16 has a relative risk contribution of
3.692; an offence of stealing in a dwelling contributes 1.881 to the relative risk;
and a conviction for shoplifting contributes 0.764. There are three previous
sentencing occasions (two more than the baseline one), and so a factor of 0.966 is
counted twice. Finally, a custodial sentence on the last sentencing occasion
contributes an additional factor of 1.454.
Some of these factors are less than one, and some are greater than one. The
convictions of unlawful sexual intercourse with an under 16-year-old and
stealing in a dwelling, together with the custodial sentence at the last
conviction all increase the relative risk, but this is mitigated by the shoplifting
charge and having more than one previous conviction. Multiplying all the
factors together gives
3.692 x 1.881 x 0.764 x 0.966 x 0.966 x 1.454
or
7.20
Therefore this offender has a risk of becoming a SSA offender that is over seven
times as great as the baseline criminal.
Several points are worth making on the general area of developing risk scores. It
was surprising that there were so many previous offences that were found to be
statistically significant. The usual pattern of re-conviction studies, where the
number of previous convictions seems to ‘swamp’ the subtleties of the effect of
different kinds of offences, was not evident here. It suggests that very particular
types of criminal career patterns involving ‘type’ (that is, the importance of
particular kinds of offences) rather than the ‘quantity’ (that is, any type of
criminal activity), characterise the greater likelihood of persons becoming
murderers, on the one hand, and committing SSA, on the other. While the
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