feature of clinical judgment in terms of predictionis the
lack of rules to integrate case information. Although this
permits flexibility, ostensible widespread applicability,
and relevance to the individual patient, there are numer-
ous problems with this approach.
First, because of the lack of rules, critics contend that
the technique generally lacks consistency because inde-
pendent clinicians may focus on dissimilar sources of
information and subsequently form disparate conclu-
sions (low interrater reliability). Second, clinicians may
or may not attend to variables that actually relate to vio-
lent behavior (low content validity). Third, either failing
to attend to important risk factors, attending to irrelevant
variables, or giving improper weight to risk factors, will
inevitably decrease the accuracy of decisions (low pre-
dictive validity). Fourth, detractors argue that unaided
clinical decision making precludes transparency of deci-
sion making, which is essential in a legal forum (low
legal helpfulness). Other factors leading to low (or at
least inconsistent) accuracy include susceptibility to
decisional biases and heuristics, failure to consider base
rate information, failure to integrate situational informa-
tion, and a lack of specificity about the criterion variable.
Research bears these weaknesses out: The accuracy of
unstructured risk assessment has been shown (a) to vary
considerably across different clinicians and (b) though
predictive of violence, to be less strongly related to vio-
lence than more systematic approaches.SSttrruuccttuurreedd RRiisskk AAsssseessssmmeenntt
In response to the shortcomings of the unstructured
clinical approach and the disquieting implications these
held for important legal decisions, researchers started to
investigate structured approaches. Contemporary struc-
tured risk assessment approaches share common fea-
tures such as (a) inclusion of a fixed set of risk factors,
(b) operational definitions of risk factors, (c) scoring or
coding procedures for risk factors, and (d) direction for
how to integrate risk factors to reach a final decision
about risk. As described below, however, there are
important differences between the two primary
approaches to structured risk assessment.Actuarial Prediction
The first structured approach that was investigated
was actuarial prediction. Technically, a prediction
approach is said to be actuarial when it uses formal
rules to combine variables or risk factors to make a
decision. This process, therefore, involves the formalapplication of a predetermined set of explicit and for-
mulaic decision rules to make a decision about the
likelihood of violence. The actuarial approach has
been described as algorithmic, mechanical, well spec-
ified, and completely reproducible. An associated,
though not defining, feature of actuarial prediction is
the use of empirical item selection; that is, the vari-
ables that comprise risk factors on an actuarial risk
assessment measure are often selected because they
demonstrated statistical associations with violence in
one (or, more rarely, two or more) specific construc-
tion or calibration sample. Another associated feature
of actuarial prediction is that the risk factors that are
derived empirically are typically weighted according
to the strength of association with violence observed
in the construction sample(s).
The primary argument in support of actuarial pre-
diction techniques is that they facilitate interrater
reliability and predictive validity, especially in com-
parison with unstructured approaches. Because actu-
arial procedures use explicit rules for combining risk
factors, they yield the same decision regardless of
who uses them (high interrater reliability), and given
the presence of the same risk factors across cases, they
yield the same outcome. Furthermore, they are trans-
parent (reviewable and accountable). Many actuarial
prediction techniques are statistically optimized
because they weigh variables according to their rela-
tionship with violence. Hence,at least in the samples
in which they were developed,they tend to have high
predictive validity in comparison with unstructured
approaches.
There is general agreement that the actuarial
approach to risk assessment yields higher predictive
accuracy than does the unstructured approach when
the two are compared for group-based (nomothetic) pre-
dictions within the same sample. Perhaps the best evi-
dence of this stems from a meta-analysis of 136 studies
conducted by William Grove and colleagues that
directly compared actuarial prediction with unstructured
clinical prediction. Actuarial prediction was more accu-
rate than clinical prediction in approximately one-third
to half of the studies. In approximately half the studies,
there was no difference in predictive accuracy. In a small
minority of studies, unstructured clinical prediction was
more accurate. On average, actuarial prediction was
more accurate than clinical prediction by an approxi-
mately 10% increase in hit rate.
Despite the important advantages of enhanced inter-
rater reliability and predictive validity that actuarial
prediction possesses, commentators have noted severalRisk Assessment Approaches——— 699R-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 699