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Assessing Risk for Violence
Stephen D. HartSimon Fraser University
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Violence
Actual, attempted, or threatened physical harm that is deliberate and nonconsenting Includes violence against victims who
cannot give full, informed consent Includes fear-inducing behavior, where
threats may be implicit or directed at third parties
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Violence as a Choice
The proximal cause of violence is a decision to act violently
The decision is influenced by a host of biological, psychological, and social factors Neurological insult, hormonal abnormality Psychosis, personality disorder Exposure to violent models, attitudes that
condone violence
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We Can’t Predict Violence…
Violence is too rare to predict with any accuracy, by any means
“Professional” decisions are particularly bad
Predictions of violence necessitate a deterministic view of behavior
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Or, Can We?
The issue of prediction is moot Don’t predict, evaluate risk (e.g., suicide)
Regardless, predictions made by professionals are reliably better than chance
The scientific literature on violence is large and growing
Any choice can be predicted
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What is Risk Assessment?
Process of understanding a hazard to limit its potential negative impact Hazard identification (which events
occur?)
Hazard accounting (how frequently?) Scenarios of exposure (under which
conditions?)
Risk characterization (conditions present?) Risk management (which interventions?)
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Nature of Violence Risk
Violence risk is a multi-faceted construct Nature: what kinds of violence might occur? Severity: how serious might the violence be? Frequency: how often might violence occur? Imminence: how soon might violence occur? Likelihood: what is the probability that violence
might occur?
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Risk is Context-Specific
We never know a person’s risk for violence; we merely estimate it assuming certain conditions Assuming institutionalization, assuming
release with supervision, assuming release without treatment for substance use…
Consequently, relative or conditional risk judgments are more useful than absolute or probabilistic risk judgments
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Goals of Risk Assessment
To make better decisions Improve consistency Protect public safety Guide intervention
Protect clients’ rightsLiability management
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Risk Characterization
Content Issues
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What to Include?
Three primary criteria Empirical (predictive accuracy) Professional (practical utility) Legal (fairness and reasonableness)
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Problems With Empirical Criterion
Not everything that is important has been proven or validated scientifically Can lead to exclusion of “good” but rare
or difficult-to-assess risk factorsPrediction cause, explanation, or
intervention Can lead to inclusion of “bad” but
common or easy-to-assess factors
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Example: The SIEVE
Age Young is badSex Male is badFacial hair Dense is badFoot sizeBig is bad
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Problems With Professional Criterion
Focus on dynamic factors may bias risk assessments Can lead to exclusion of “good” but
static or easy-to-ignore factorsConventional wisdom of
professionals may be plain wrong Can lead to inclusion of “bad” but vivid
or dramatic factors
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Example: Clinical Intuition
Depression Present is goodAnxiety Present is goodIntelligence High is goodRorschach Seeing viscera is bad
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Problems With Legal Criterion
Useful for excluding risk factors, but not for including them
It can be argued that almost any risk factor is unfair or unreasonable in some respect
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Risk Characterization
Procedural Issues
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Conventional Approaches
Professional judgment Unstructured or “clinical” Anamnestic (see Melton et al., 1997) Structured (e.g., HCR-20, SVR-20)
Actuarial decision-making Psychological tests (e.g., MMPI-2, PCL-R) Risk scales (e.g., VRAG, RRASOR)
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Professional Judgment
Most commonly-used method for violence risk assessment Familiar to professionals Familiar to courts and tribunals
General strengths of method Flexible (easy administration) Requires limited training and technology Person-centered (“idiographic”)
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Unstructured: Features
No constraints on evaluation Any information can be considered Information can be gathered in any
mannerNo constraints on decisions
Information can be weighted and combined in any manner
Results can be communicated in any manner
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Unstructured: Limitations
No systematic empirical support Low agreement (unreliable) Low accuracy (unvalidated) Foundation is unclear (unimpeachable)
Relies on charismatic authorityDecisions are broad bandwidthFocus is on culpability, not action
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Anamnestic: Features
Imposes minor structure on evaluation Must consider, at a minimum, nature and
context of past violenceAction-oriented
Logically related to development of risk management strategies
Consistent with “relapse prevention” or “harm reduction” approaches
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Anamnestic: Limitations
Unknown reliabilityUnknown validityAssumes that history will repeat
itself Violent careers are static Violent people are specialists
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Structured: Features
Imposes major structure on evaluation Must consider, at a minimum, a fixed and
explicit set of risk factors Specifies process for information-gathering
Imposes minor structure on decision Specifies language for communicating
findingsAction-oriented
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Structured: Limitations
Requires “retooling” of evaluation process Systematized information-gathering New training and technology
Justification for imposing structure requires inductive logic (faith) What works elsewhere will work here Professional discretion is appropriate
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HCR-20
HCR-20, version 2 Webster, Douglas, Eaves, & Hart (1997) Designed to assess risk for violence in
those with mental or personality disorders
10 Historical, 5 Clinical, and 5 Risk Management factors
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Applications
Assess clinical evaluations of violence risk across a broad range of populations and settings Civil and forensic psychiatric, correctional Institution, community
Monitor clinical and situational factors that may be relevant to violence
Guide risk management strategies
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Conceptual Basis
Intended to bridge clinical and empirical domains and knowledge bases Evidence-based risk assessment
Content determined rationally Based on reviews of scientific and
professional literatures Not optimized on a particular sample
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Temporal Organization
P as t (S ta tic )D ocu m en ted
(1 0 Item s)
H is to rica l
P resen t (D yn am ic )O b served(5 Item s )
C lin ica l
F u tu re (S p ecu la tive )P ro jec ted(5 Item s )
R isk M an ag em en t
V io len ce R isk
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Historical Factors
Previous violenceYoung age at first
violenceRelationship
instabilityEmployment
problemsSubstance use
problems
Major mental illness
PsychopathyEarly
maladjustmentPersonality
disorderPrior supervision
failure
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Clinical & Risk Management Factors
Lack of insightNegative attitudesActive symptoms
of major mental illness
ImpulsivityUnresponsive to
treatment
Plans lack feasibilityExposure to
destabilizersLack of personal
supportNoncompliance with
remediation attempts
Stress
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Actuarial Decision-Making
Commonly-used adjunctive method for violence risk assessment Familiar to some professionals
(psychologists) Somewhat familiar to courts and tribunals
General strengths of method Highly structured/systematic (“objective”) Empirically-based (“scientific”)
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Psychological Tests: Features
Measure some disposition that predicts violence, according to past research
Reliability and validity of test-based decisions has been evaluated
Imposes major structure On some part of the evaluation process On some part of the decision-making
process
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Psychological Tests: Limitations
Require professional judgment Which tests to use How to interpret scores
Justification of use requires inductive logic Our population is like theirs Our use of the test is like theirs
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PCL:SV
Symptom construct rating scale requires clinical / expert judgment based on “all data”
Data obtained from two primary sources: review of case history (required) interview / observation
(recommended)
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PCL:SV: Items
Part 1SuperficialGrandioseDeceitfulLacks remorseLacks empathyDoesn’t accept
responsibility
Part 2 ImpulsivePoor behavioral controlsLacks goals IrresponsibleAdolescent antisocial
behaviorAdult antisocial
behavior
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PCL: Summary #1
The correlation between the PCL and violent recidivism averages about .35 Regardless of length of follow-up Even in sex offenders, forensic patients,
women, delinquents — even in nonviolent, nonpsychopathic offenders
Association is quasi-linear (positive and monotonic)
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PCL: Summary #2
Among psychopaths (e.g., PCL-R > 30) released from prison, the 5-year violent reoffense rate is about 70% Versus about 30% in low group (< 20)
and 50% in medium group (21-29) Versus low group, psychopaths are at
very high risk for reoffense (rate ratio = 2x to 3x; odds ratio = 5x to 10x)
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PCL: Summary #3
Psychopaths not only commit more violence, they commit different kinds of violence
The violence of psychopaths often has unusual or atypical motivations Instrumentality/gain Impulsivity/opportunism Sadism
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PCL: Conclusions
Psychopathy must be assessed as part of comprehensive violence risk assessments
The presence of psychopathy compels a conclusion of high risk
The absence of psychopathy does not compel a conclusion of low risk
Psychopathy must be assessed by trained professionals using adequate procedures
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Decision Tree
Homicidal/suicidal?
NO
YES High Risk
Psychopathic?(e.g., PCL-R > 30)
NO
High Risk
Assess other factors(e.g., HCR-20)
Sexual sadism?
NO
High RiskYES
YES
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Risk Scales: Features
Designed solely to predict an outcome
High-fidelity Optimized for specific outcome, time
period, population, and contextImpose rigid structure
On all of the evaluation process On all of the decision-making process
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Risk Scales: Limitations
Still require professional judgment Which scales to use How to interpret scores
Justification of use still requires induction Our population is like theirs Our use of the test is like theirs
Results may be easily misinterpreted Pseudo-objective, pseudo-scientific
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VRAG
Violence Risk Appraisal Guide Quinsey et al. (1998) Constructed in adult male patients
assessed or treated at a maximum security hospital
12 items weighted according to ability to postdict violence over 7 year follow-up
Total scores divided into 9 bins, with estimated p(violence) from 0% to 100%
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VRAG Items
PCL-R scoreElem. school
problemsPersonality disorderAge (—)Separated from
parents under age 16Failure on prior
conditional release
Nonviolent offense history
Never marriedSchizophrenia (—)Victim injury (—)Alcohol abuseFemale victim (—)
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VRAG: Potential Problems
The VRAG is, in essence, a history lesson:
What if patient profile changes?What if p (violence) changes?What if the assessment context
changes?
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VRAG: Actual Problems?
Paul Bernardo is a convicted serial murderer (3 sexual homicides) and serial rapist (75 known rapes)
Currently serving life imprisonment for murder, and an indeterminate sentence for the rapes
VRAG completed on the basis of case history data
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Bernardo’s VRAG Results
PCL-R score +4 Elem. school… -1 Personality disorder +3 Age 0 Separated from… -2 Failure on prior… 0 Nonviolent offense… -2 Marital status -2 Schizophrenia +1 Victim injury -2 Alcohol abuse +1 Female victim -1
Total: -1
Bin #: 4
p(viol): 17% - 31%
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Problems With All
Focus on negative characteristics “Sticky” labels What about strengths (resources,
“buffer” factors)? Risk assessment risk management
What to do with high-risk individuals?Quality control
Who will assess risk, and how?
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Risk References
Boer, D. P., Hart, S. D., Kropp, P. R., & Webster, C. D. (1997). Manual for the Sexual Violence Risk-20: Professional guidelines for assessing risk of sexual violence. Burnaby, British Columbia: Simon Fraser University.
Grove, W. M., & Meehl, P. E. (1996). Comparative efficiency of informal (subjective, impressionistic) and formal (mechanical, algorithmic) prediction procedures: The clinical-statistical controversy. Psychology, Public Policy, and Law, 2, 293-323.
Kropp, P. R., Hart, S. D., Webster, C.W., & Eaves, D. (1995). Manual for the Spousal Assault Risk Assessment Guide, 2nd ed. Vancouver, BC: British Columbia Institute on Family Violence.
Meehl, P. E. (1996). Clinical versus statistical prediction: A theoretical analysis and a review of the literature. Northvale, NJ: Jason Aronson. (Original work published in 1954.)
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Risk References (cont.)
Melton, G. B., Petrila, J., Poythress, N. G., & Slobogin, C. (1997). Psychological evaluations for the courts: A handbook for mental health professionals and lawyers (2nd ed.). New York: Guilford.
Quinsey, V. L., Rice, M. E., Harris, G. T., & Cormier, C. (1998). Violent offenders: Appraising and managing risk. Washington, DC: American Psychological Association.
Webster, C. D., Douglas, K. S., Eaves, D., & Hart, S. D. (1997). HCR-20: Assessing risk for violence, version 2. Burnaby, British Columbia: Simon Fraser University.
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But How Accurate Are
Characterizations of Risk?
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A Complex Phenomenon
Studying the accuracy of risk characterizations is difficult due to the complexity of… The characterizations The violence The follow-up Indexes of accuracy
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The Characterizations
Evaluator: Professional vs. researcher; novice versus expert
Process: Clinical vs. actuarial, contextual vs. context-free
Timing: Admission vs. discharge, static vs. dynamic
Metric: Uni- vs. multi-dimensional, categorical vs. continuous
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The Violence
Direction: Self vs. others, acquaintances vs. strangers
Nature: Instrumental vs. reactiveSeverity: Threats vs. battery vs.
homicideFrequency: Single vs. multiple eventsContext: Situational precipitants or co-
factors
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The Follow-Up
Data source: Patient vs. collaterals vs. records
Time at risk: Weeks vs. months vs. years
Interventions: Dynamic factors, life events
Monitoring: Continuous vs. endpoint
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Indexes of Accuracy
Comparison group: Other patients vs. normals
Statistic: Uni- vs. multi-variate, timeWeighting of errors: Equal vs.
differential Interpretation: Chance vs. status quo
vs. perfection
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OutcomePrediction Not Violent Violent
Low Risk High Risk
Science Responds to Complexity
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Example: Psychopathy
OutcomePrediction Not Violent Violent
Low Risk(Non-psychopath)
90 24
High Risk(Psychopath)
12 40
Harris, Rice, & Cormier (1991)
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Example (cont.)
In this study... Accuracy of positive predictions is 77% Accuracy of negative predictions is 79% Overall accuracy is 78% Chance-corrected agreement is 53% Correlation is .53 Odds ratio is 12.5
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Example (cont.)
So, how did we do? Relative to chance: Great! Relative to perfection: Awful! Relative to the status quo: ???
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What is the status quo?
Predictions of violence using the PCL-R typically have an effect size (r) of about .35; the average effect size for psychosis is about .30
An effect size of .40 may be the “forensic sound barrier”
But what is the status quo in other human endeavors?
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Meta-Meta-Analysis
Lipsey & Wilson (1993) reviewed 302 meta-analyses
Determined typical effect sizes for psychological, educational, and medical interventions
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Psychological Interventions
CBT — depression .44Psychotherapy — any .39Correctional programs (youths) .23
— any Diversion (youths) — recidivism.20Correctional treatment (adults) .12
— any
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Educational Interventions
Small classes — class climate .26Tutoring — grades .20Small classes — grades .10Media campaigns — seatbelt use
.06
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Medical Interventions
Speech therapy — stuttering .54Bypass surgery — angina pain .37Cyclosporine — organ rejection.15Bypass surgery — mortality .07ASA — heart attack .04
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Violence Predictions in Context
Speech therapy — stuttering .54CBT — depression .44Bypass surgery — angina pain .37Psychopathy — violence .35Psychosis — violence .30Small classes — class climate .26
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Conclusions
Violence predictions, on the whole, are just as good as most other human prognostications
Consider other fields... Stock analysts Meteorologists Fire inspectors Structural engineers
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Risk Assessment:
Reports and Testimony
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General Issues
Acknowledge professional qualifications But, less important than approach used
Acknowledge limits of information base But, comprehensiveness depends on context
Explain risk factors considered Empirical, professional, legal justification
Acknowledge uncertainty of “predictions”
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Do Don’t
Use multiple approaches
Make relative or conditional risk judgments
Make detailed risk management recommendations
Rely on a single approach
Make absolute or probabilistic risk judgments
Ignore the issue of what can or should be done
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Special Issues: Professional
Report should tell a story Summarize the circumstances of past
violence and any recent changes in them Describe the likely nature and context
(scenarios) of future violence Identify factors that may increase risk and
therefore serve as flags for re-assessment Recommend, evaluate, and prioritize risk
management strategies
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Cross-Exam: Professional
What, if any, is the basis of your expertise in the assessment of violence risk?
What is the scientific basis for your decision (not) to follow these procedures?
What is the scientific basis for your decision (not) to consider these factors?
Can you state with any reasonable degree of scientific certainty the likelihood that X will be violent?
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Special Issues: Actuarial
Report should provide full interpretation of test scores Be familiar with research supporting the
test’s reliability and validity Discuss general limitations of the test Discuss limitations of the test in this
case
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Cross-Exam: Actuarial
Isn’t it arbitrary to consider risk factors such as A, B, and C, but to ignore D, E, and F?
Is there any scientific evidence that scale Z predicts outcome Y in patients at this clinic?
How do you know that predictions using scale Z are accurate for Mr. X?
By using scale Z, aren’t you simply relying on statistical profile evidence?
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Contact Information
Stephen D. Hart, Ph.D.Department of PsychologySimon Fraser UniversityBurnaby, British ColumbiaCanada V5A 1S6Tel: 604.291.5485 / Fax: 604.291.3427E-mail: [email protected]: www.sfu.ca/psychology/groups/faculty/hart