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

INTRODUCTION
Many individuals who are present on the OI have been convicted of only a single
offence and a high proportion of these will have desisted from crime. The
comparison group was therefore chosen to be made up of active but less serious
offenders. In this context, an active offender was one who had been convicted of an
offence in the same calendar year as the serious offender (the index conviction).
For murder cases, control individuals were selected who had not been convicted for
any offence relating to murder (that is, murder, manslaughter, infanticide, attempted
murder or threats to kill) at the index conviction. Additionally, like the case, the
control should also not have been convicted for murder in their previous criminal
history. Control group cases with previous convictions for other offences relating to
murder (i.e. manslaughter, infanticide, attempted murder or threats to kill) were,
however, included.
In a similar way, the relevant control group offender for a SSA case was an active
offender who had not committed a serious sexual offence as their index offence. This
definition excluded offenders with a conviction for any type of rape (including
attempts) of males or females of any age, indecent assault against females aged 16 or
over who received any length of custodial sentence, all indecent assault against females
under 16, other serious sexual offences against children or males, or incest. The offence
of murder was also excluded. Offenders were additionally excluded from the control
group on the basis of the following previous convictions: murder; (completed) rape of a
female of any age; indecent assault of a female under 16; and indecent assault of a
female aged 16 or over who received any length of custodial sentence.
Those convicted of indecent assault of a female aged 16 or over who received
shorter custodial sentences (that is, not reaching the thresholds defining a ‘serious’
offence identified in Appendix A), were neither used as cases nor controls. This was
to allow some leeway in the definition of what separates a serious indecent assault of
an adult female from a less serious indecent assault. However, those previously
convicted of indecent assault of an adult female who did not receive a custodial
sentence were available as cases or controls. This issue becomes particularly
important in the analyses that follow.
Control groups can produce misleading results. For example, if a control group of
offenders not convicted of murder reveals that previous violence offences are a risk
factor for murder, it is unclear whether the risk factor is specific to murder or
represents a general risk factor for any serious violent conviction (of which murder
is the extreme example). The control group, after all, is likely to be dominated by
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