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Predicting violent reconvictions using the HCR-20

  • Nicola S. Gray (a1), John Taylor (a2) and Robert J. Snowden (a3)

Risk assessment of future violent acts is of great importance for both public protection and care planning. Structured clinical assessments offer a method by which accurate assessments could be achieved.


To test the efficacy of the Historical, Clinical and Risk Management Scales (HCR–20) structured risk assessment scheme on a large sample of male forensic psychiatric patients discharged from medium secure units in the UK.


In a pseudo-prospective study, 887 male patients were followed for at least 2 years. The HCR-20 was completed using only pre-discharge information, and violent and other offending behaviour post-discharge was obtained from official records.


The HCR–20 total score was a good predictor of both violent and other offences following discharge. The historical and risk sub-scales were both able to predict offences, but the clinical sub-scale did not produce significant predictions. The predictive efficacy was highest for short periods (under 1 year) and showed a modest fall in efficacy over longer periods (5 years).


The results provide a strong evidence base that the HCR–20 is a good predictor of both violent and non-violent offending following release from medium secure units for male forensic psychiatric patients in the UK.

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Corresponding author
Nicola S. Gray, School of Psychology, Cardiff University, Cardiff CF10 3AT, UK. Email:
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2 Monahan, J, Steadman, HJ, Silver, E, Appelbaum, P, Robbins, P, Mulvey, E, Roth, L, Grisso, T, Banks, S. Rethinking Risk Assessment: The MacArthur Study of Mental Disorder and Violence. Oxford University Press, 2001.
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4 Webster, CD, Douglas, KS, Eaves, D, Hart, SD. HCR-20: Assessing Risk for Violence (Version 2). Simon Fraser University, 1997.
5 Gray, NS, Hill, C, McGleish, A, Timmons, D, MacCulloch, MJ, Snowden, RJ. Prediction of violence and self-harm in mentally disordered offenders: a prospective study of the efficacy of HCR-20, PCL–R and psychiatric symptomology. J Consult Clin Psychol 2003; 71: 443–51.
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Predicting violent reconvictions using the HCR-20

  • Nicola S. Gray (a1), John Taylor (a2) and Robert J. Snowden (a3)
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The HCR-20 Catch-22

Neelom Sharma, Trainee Psychiatrist (ST3)
21 August 2008

Gray et al have written a thought-provoking article on efficacy of the HCR-20 violence risk assessment tool, strengthening the evidence base for using this tool actuarially to predict long-term violence risk. It is heartening that this evidence base is now emerging, given the widespread use of the HCR-20 in UK forensic mental health.

However, the fundamental problem with this type of research is that an efficacy study (i.e. measuring the effect of the HCR-20 in experimentalconditions) does not measure the effectiveness of a clinical tool. This study used case notes to construct HCR-20s for patients. It is therefore unsurprising that the clinical domain did not produce significant predictions, as reviewing case notes does not meaningfully replicate the clinical setting.

Webster et al’s manual for using the HCR-20 states that, “for most contexts in which the HCR-20 has a foreseeable use, the person will be available for interview.” In this pseudo-prospective study, this was not the case. The HCR-20 manual adds, “In most cases, file review, interview and testing should be adequate to complete the HCR-20. However, particularly for the risk management section, consultation with colleaguesresponsible for treatment or community release plans will likely be needed.” Thus the validity of risk items in HCR-20s completed only by case-note review is also questionable. As those who complete the HCR-20 routinely will testify, it is typically constructed by multidisciplinary discussion among a group of professionals who are familiar with the patient.

It is easy to see why Gray et al adopted this efficacy-based approach; the Catch-22 is that an effectiveness study would be ethically difficult to perform, and expose the clinical team to potential criticism.Clinically, those deemed to be at high risk of violent reoffending (i.e. those with high HCR-20 scores in this paper) require aggressive risk management, which may involve ongoing detention. Thus an effectiveness study which showed that HCR-20 had high predictive validity would suggest an ineffective clinical team, who had allowed patients to reoffend despiteidentifying the risk beforehand.

There are other methodological difficulties in this paper. For example, it is stated that, “Cases of patients reconvicted for a non-violent offence were removed from the analysis of violent offences from the time the non-violent offence occurred, as these individuals might no longer have been at liberty to commit further offences.” While this has face validity, it is not an exclusion criterion based on facts (e.g. police or health records), but on untested hypothesis. It is also the onlyexclusion criterion; many other reasons for variations in violent reconviction rates are not considered (e.g. hospital readmission). This issue could have been addressed by obtaining follow-up data.

In summary, HCR-20 is a useful tool, and there is a growing evidence base (including this paper) to suggest it can be used in a number of different ways, including actuarially. Unfortunately, methodological flawsand the use of a clinical tool in a non-clinical manner limit the strengthof the evidence presented here.

Reference:Webster CD, Douglas KS, Eaves D, Hart SD. HCR–20: Assessing Risk for Violence (Version 2). Simon Fraser University, 1997
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