20 años de progreso en atención a violencia sexual

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10.1177/0886260504267740JOURNALOFINTERPERSONALVIOLENCE/February2005Hanson/PROGRESSINVIOLENCERISKASSESSMENT

Twenty Years of Progress

in Violence Risk Assessment

R. KARL HANSON

Public Safety and Emergency Preparedness Canada

Violence risk assessment has advanced considerably in the last 20 years. In the

1980s, leading professionals questioned the very possibility of valid violence risk

assessments; now, many of the major risk factors have been identified, and profes-

sionaldebate focuses onhow best to combine these riskfactorsinto meaningful eval-

uations. An important contributor to this advance in knowledge has been the rise of meta-analytic reviews. Through quantitative summaries, the cumulative findings of

small,potentially insignificantstudies haveprovided importantanswers to questions

concerning the effective assessment and treatment of violent offenders.

Keywords: violence; risk prediction; meta-analysis

Assessing the risk of violence has always been one of the central tasks for

those involved in the management of offenders in the criminal justice and

mental health systems, but it has never been easy. As a doctoral student in

clinical psychology, I was taught that knowledge of recidivism prediction

was sufficiently poor that professionals should refrain from making long-

term predictions. Short-term predictions of violence were permitted, not

because experts were substantially better at this task, but because the conse-

quences of erroneous short-term predictions were more tolerable to the cli-

ents (e.g., they may stay an extra week in a hospital). Much of the pessimism

about risk assessment was derived from Monahan’s (1981) important mono-

graph and the earlier study of the Baxstrom patients in which the sudden

release of dangerous psychiatric patients failed to produce the expected

carnage (Steadman & Cocozza, 1974).

It is still easy to find professionals whoquestion thevalidity of risk assess-

ments for violence, but the tone of the research literature has changed. Jour-

nals arenow filled witharticles in which long-term violent recidivism is pre-

dicted with moderate to high accuracy. Rather than questioning whether

212

Author’s Note: The views expressed are those of the author and do not necessarily those of Public Safety and Emergency Preparedness Canada.

JOURNAL OF INTERPERSONAL VIOLENCE, Vol. 20 No. 2, February 2005 212-217

DOI: 10.1177/0886260504267740

© 2005 Sage Publications



violence can be predicted, researchers are debating the best methods of risk

assessment. Monahan andSteadman haveeven proposed their own approach

to violence risk assessment (Steadman et al., 2000).

This is a remarkable change. Theprogress in violence risk assessment has

been motivated, in part, by social policy in Canada and the United Statesthat

has increasingly emphasized community safety as the fundamental goal of

intervention with offenders (Petrunik, 2003). The initial success of empiri-

cally based risk assessment was used to justify legislation that included risk-

based decisions (e.g., dangerous offender designations in Canada;

postsentence detention of high-risk sexual offenders in the United States),

which, in turn, hasencouraged further research on risk assessment. As a con-

tributor to the risk research literature, I have come to expect courts to care-

fully scrutinize my work with lawyers alternately claiming that my work iseither accepted fact or the mushiest of pseudo-science.

The progress in violence prediction can also be attributed to the excep-

tional efforts of some very talented researchers.RobertHare’s doggedefforts

to establish psychopathy as a reliable and valid clinical construct produced

the first big successes in violence risk prediction (e.g., Forth, Hart, & Hare,

1990). Harris, Rice, and Quinsey deserve much credit for documenting how

empirically derived combinations of common clinical variables can be used

to predict long-term violent recidivism (Quinsey, Harris, Rice, & Cormier,

1998). Their work builds upon a long tradition within criminology of using

actuarial instruments to predict general criminal recidivism (e.g., Burgess,

1928; Nuffield, 1982).

Another important group of contributors has been Andrews, Bonta, and

Gendreau whohaveemphasized theneed to distinguish between types of risk factors (e.g., Andrews & Bonta, 2003; Gendreau, Little, & Goggin, 1996).

Static, historical risk factors canbe useful for the purpose of pure prediction,

but knowledge of dynamic (changeable) risk factors is required to know

where to intervene. The risk prediction instrument based on their social psy-

chological model of crime, the Level of Service Inventory–Revised (LSI-R;

Andrews & Bonta,1995), is themost widelyused andbest validatedmeasure

of general criminal recidivism.

The 1990s saw the rapid introduction of empirically based violence risk

assessment tools. These included structured professional guidelines (such as

the Historical, Clinical, Risk–20 [HCR-20]; Webster, Douglas, Eaves, &

Hart, 1997) as well as fully actuarial measures (e.g., the Violence Risk

Appraisal Guide [VRAG]; Harris, Rice, & Quinsey, 1993). Specialized

measures were developed for subpopulations such as sexual offenders

(Epperson, Kaul, & Huot, 1995), wife assaulters (the Spousal Assault Risk

Assessment Guide; Kropp, Hart, Webster, & Eaves, 1999), young offenders

Hanson / PROGRESS IN VIOLENCE RISK ASSESSMENT 213



(Hoge & Andrews, 2002), and young sexual offenders (Prentky, Harris,

Frizzell, & Righthand, 2000).

The validation research has typically found that all these measures show

moderate accuracy in predicting violent recidivism, the predictive accuracy

of the measures are similar, and all the measures are substantially corre-

lated with each other. Knoner, Mills, and Reddon (in press) even found that

randomly selected items from commonly used risk scales (VRAG, LSI-R,

Psychopathy Checklist–Revised, General Statistical Information on Recidi-

vism) predicted recidivism as well as the individual scales. The same vari-

ables tend to predict general recidivism and violent recidivism (Gendreau,

Goggin, & Smith, 2002; Kroner & Mills, 2001) as well as sexual recidivism

(Hanson & Bussière,1998; Hanson& Morton-Bourgon, 2004). Sexual devi-

ance, however, may be an exception in that it predicts sexual recidivism butnot other forms of criminal recidivism.

WHAT WE NEED TO KNOW

Although we know that these risk scales predict violence, we know less

about what they are measuring. One position is that they differentiate a per-

sistently criminal subgroup (antisocial taxon) fromnormal offenders(Harris,

Rice, & Quinsey, 1994). The other dominant position, led by Andrews and

Bonta (2003), is that the scales identify conceptually distinct, but correlated,

risk factors thereby creating a continuum of risk potential. The resolution of

these positions is important for the evaluation of change (e.g., conditional

release decision, treatment outcome). For evaluators who perceive their roleas differentiating high-risk offenders from low-risk offenders, dynamic

(changeable) risk factors are only relevant for identifying the timing of

reoffending. In contrast, evaluators who believe that offenders can change

need to consider how changes on enduring risk factors should influence

medium- to long-term recidivism potential.

The available research suggests that potentially changeable factors (e.g.,

attitudes, lifestyle instability) contribute information to risk potential that is

not captured by purely static, historical factors (Beech, Fisher, & Thornton,

2003; Hanson & Harris, 2000; Mills, Kroner, & Hemmati, 2003). There is

also some evidence that changes on these criminogenic needs correspond

to changes in recidivism potential (Andrews & Bonta, 2003, pp. 249-

250; Beech, Erikson, Friendship, & Ditchfield, 2001; Marques, Day,

Wiederanders, & Nelson, 2002). There is much to learn, however, aboutcombining static and dynamic risk factors into an overall evaluation.

214 JOURNAL OF INTERPERSONAL VIOLENCE / February 2005



LEARNING THROUGH META-ANALYSIS

The major methodological innovation in the last 20 years has been the

routine useof quantitative summaries of researchfindings.Quantitative sum-

maries of single studies were used in the early 20th century by Karl Pearson

and Ronald Fisher (Olkin, 1995), but it was not until Glass’s (1976) study of

psychotherapy outcome that the term meta-analysis was introduced to the

professional literature and caught the attention of social scientists (Hunt,

1997). The results of a single study can be interesting, but increased confi-

dence can be placed in the results when the same relationships are found in

many studies. Consequently, it is not surprising that meta-analysis is nowthe

accepted method of answering questions concerning the magnitude and

direction of empirical relationships (Cooper, 2003).In thefieldof crimeandviolence,meta-analyses haveanswered important

questions concerning the effectiveness of correctional treatment (Andrews

et al., 1990) and the prediction of recidivism among general offenders

(Gendreau et al., 1996), mentally disordered offenders (Bonta, Law, &

Hanson, 1998), and sexual offenders (Hanson & Bussière, 1998). Whenever

they are available, meta-analyses should be the starting point for researchers

and policy makers wishing to learn about the empirical findings in particular

subject areas.When researchers do nothave access to a meta-analysis of pre-

vious research, they should conduct one prior to conducting a new study.

Science is a socialactivity. Unfortunately, students in most research meth-

ods courses are only taught how to conduct single studies and do not learn

how to statistically compare their findings to the findings of other research-

ers. Not surprisingly, journals are filled with tests of the null hypothesis(which is never true) and neglect more useful statistics such as effect sizes

and confidence intervals. Progress during the next 20 years will be acceler-

ated as individual researchers increasingly think like meta-analysts and rou-

tinely consider their findings as only one addition to cumulative knowledge

(Lau, Schmid, & Chalmers, 1995).

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R. Karl Hanson completed his Ph.D. in clinical psychology from the University of

Waterloo (Ontario)in 1986afterwhichhe conductedclinicalwork withoffendersfor the

Ontario Ministry of Correctional Services and the Clarke Institute of Psychiatry. Since

1991,he hasbeena seniorresearch officerwith PublicSafetyand Emergency Prepared-

ness Canada, specializing in research on sexual offenders and abusive men.


20 años de progreso en atención a violencia sexual

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