Discussion Papers |
Expert witness evidence rules and PTSD(April 2012)Authored by Paul Luke Bodisco (Barrister, Supreme Court of NSW) & Martha Knox-Haly ( Workplace Research Centre, University of Sydney) Abstract The article analyses the challenges for the legal profession in evaluating the evidence of mental health professionals in a medicolegal context. The paper outlines six criteria that clinical and legal professionals must consider in developing this evidence. These criteria concern establishment of legitimacy of credentials, training and experience of experts and demonstration of scientific methodology underpinning expert evidence. The paper also considers idiopathic versus nomothetic aspects of forensic psychology, as well as best evidence practice for diagnosis and assessment of post traumatic stress disorder (PTSD); and the legal experts’ role in establishing a factual basis to determine acceptance of PTSD as a diagnosis. The final points for consideration are the role of premorbid personality in vulnerability to PTSD and assessment of malingering in PTSD. Introduction Crown and Lee have referred to the contrast between the medical profession which actively debates best evidence practice with “the almost complete absence of discussion of best evidence practice within the legal profession.” There is also a relative silence in law schools on the evaluation and teaching of scientific method. It is a surprising deficit given the increasing reliance of Tribunals of Fact on expert evidence. The gap becomes particularly problematic in the area of evidence from mental health experts which can never be absolute; despite legal requirements for charges to be proved beyond reasonable doubt. The present paper tries to partially redress these difficulties by focusing on the most commonly litigated and contested mental health condition of Post Traumatic Stress Disorder. The popularity of Post Traumatic Stress Disorder in litigation stems in part from it’s aetiology. Its cause is often associated with events that may often be defined as criminal or negligent. Freckleton compared Post Traumatic Stress Disorder to HIV caused by blood transfusions, or RSI and lung disease caused by passive smoking. All these disorders were “discovered by private law and later becoming the subject of public health intervention and regulation”. Indeed it is worth noting that the diagnostic criteria from the DSM-IV-TR require that “the person experienced, witnessed or was confronted with an event or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of the self or others.” P TSD is mostly diagnosed in civil, criminal and compensation tribunals; and there is a concern that Post Traumatic Stress Disorder is vulnerable to misdiagnosis, over diagnosis or coaching. Any clinician attempting to establish a technically rigorous diagnosis of Post Traumatic Stress Disorder for medico-legal purposes will face a number of unique challenges. It assumed that most legal professionals engaging a clinician for medicolegal purposes would normally cover some, but not all of the challenges in pre-court preparation. These challenges fall into six broad categories:
Establishment of Legitimacy for Experts
According to no less a source than Wikipaedia – and confirmed somewhat in the writing of Sir Karl Popper - scientific method refers to the process of collecting data that is observable, measurable and empirical. The foundation for data collection needs to be framed with the generation of hypotheses (propositions) that are subsequently tested or falsifiable through systematic enquiry and research. The concept of objectivity and systematic approaches are seen as being important to the reduction of bias. Methodology must be adequately documented so as to facilitate replicability of results; and the nature of hypothesis generation must be grounded within theory which provides a coherent structure for integrating hypotheses. Finally there must be a practice of full disclosure to establish transparency of research methodologies and suitability of statistical measures. Psychological research on Post traumatic stress disorder comes largely from two main self report measures or essentially survey based data; with a secondary contribution from the field of biochemistry which focuses on the psychobiology of PTSD. There is a long list of case law decisions that provide useful guidelines in evaluating the probative value of survey data and the application of scientific method to survey data. Specifically the survey sample needs to be representative of the population of interest, and sampled sub-populations must be representative (see Ritz Hotel Ltd v Charles of the Ritz (1988) 15 NSW LR 158; Joseph E Seagram & Sons Ltd v Seagram Real Estate Ltd (1990) 33 CPR (3d) 454 at 473). This means that the demographic structure of the survey must mirror the demographic profile of the broader population. The sample needs to be of a sufficient size as to be representative (Imperial Group Plc v Philip Morris Ltd (1984) RPC 293). There must be full disclosure around the number of samples, size of samples and how sampling was conducted (Imperial Group Plc v Philip Morris Ltd (1984) RPC 293). There is a conflict between the Australian Psychological Society Code of Ethics with the requirement of informed consent, and the conclusions listed in State Government Insurance Corp v Government Insurance Office (NSW) (1991) 101 ALR 259. Informed consent requires that survey respondents be advised as to who has commissioned research, the purpose of research, the limits of confidentiality and the assurance that information will be kept secure. Exceptions to information being kept secure include circumstances where there are health and well being concerns, written consent has been provided for release of a report to a third party or that information has been subpoenaed. State Government Insurance Corp v Government Insurance Office (NSW) (1991) 101 ALR 259 held that disclosure of the company commissioning the survey should not be made to interviewees, and that interviewers should have no knowledge of the survey purpose or associated litigation. Resolution of this conflict is important as the expert’s compliance with a Profession’s Code of Ethics goes directly to the credibility of that expert. A conundrum posed by the reliance on scientific method The emphasis bought by Daubert v. Merrell Dow Pharmaceuticals, Inc . and Kumho Tire Co. v. Carmichael5 on the concept of scientific methodology presents a particular problem for mental health clinicians. There is no shortage of large scale epidemiological studies and reviews in the area of PTSD research; nor are there difficulties with being able to extrapolate material from this to comment on the broad phenomenon of PTSD. Rather the problem arises when an expert is called upon to comment on the case of an individual, this is what Slobogin refers to the “idiopathic” and “nomothetic” aspects of forensic psychology. Assessment and treatment of PTSD cases can involve a large measure of intuitive judgment and art, rather than science. For example, Slobogin observes that “insanity” describes as a normative state that cannot possibly be directly observed. The concerns of psychologists such as Slobogin and Daniel Fishman are that must of psychology is positivist, (i.e. it has been traditionally concerned with the discovery of universal laws of human behaviour derived from behavioural observation and statistical analysis). This is a very far call from the decision making process that a clinician engages in. The positivist paradigm is based on nomothetic or group based research grounded in general theory. Fishman argues that human behaviour is best studied on a case by case basis through thick description and systematic investigation; rather than grand research designs. Fishman suggests that peer reviewed model forensic case reports be collected in a computerized data base, along with a legal disposition of the case. Large scale nomothetic studies “showing statistically descriptive, probabilistic relationships that add to the interpretation of individual The need to define a traumatic event Because a diagnosis of PTSD requires the occurrence of a traumatic event, it can be argued that the factual basis for the occurrence and existence of a traumatic event needs to be proved prior to such a diagnosis being undertaken. To this end the judgments in the cases of Paric v John Holland (Constructions) Pty Ltd (1985) 59 ALJR 844 at 846, Paric v John Holland Constructions Pty Ltd (1985) 62 ALR 85, 87, Ramsay v Watson (1961) 108 CLR 642 , Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705, [64] , ASIC v Rich (2005) NSWCA 152 would all appear to be pertinent in drawing conclusions around the admissibility of expert opinion on a diagnosis of PTSD. These cases articulated the need for pertinent facts to be proved for expert opinion on those facts to be regarded as admissible. In methodological terms the major epidemiological studies of PTSD prevalence have relied on an operationalisation of DSM-IV-TR critieria. Prevalence estimates of PTSD are also significantly reduced when clinical significance criterion (i.e. PTSD symptoms must be of sufficient severity to cause significant distress or impairment) are included When clinical significance criterion was retrospectively factored into analysis of data from the Australian National Survey of Mental Health and Well Being, the prevalence of PTSD dropped by around 24%. Breslau and Alvarado assessed PTSD prevalence in Detroit Michigan amongst a representative sample of 2181 respondents. The authors utilized 19 traumatic events which were based on a recasting of DSM-IV criteria. In the Breslau and Alvarado study the conditional probability of PTSD given exposure to trauma given exposure to trauma was reduced by approximately 30%. The establishment of generally acceptance of diagnostic and treatment procedures for PTSD The general acceptance test was derived from the 1923 decision on the admissibility of polygraph evidence in Frye v. United States, 67. This test requires that expert testimony not only assist the fact finder, but that it’s theoretical and methodological foundations be generally accepted in the relevant field. From a mental health professional’s perspective, there are a number of ways in which general acceptance amongst a profession can be established. These include surveying of usage amongst a profession, empirical evidence that a treatment approach is effective or endorsement by a professional association that a treatment approach represents best practice. Cochrane Collaborations represent the highest form of evidence in psychological research. The Collaborations are a series of international projects which examine the cumulative evidence presented by studies utilizing random controlled trials. Best evidence practice around assessment and treatment of PTSD. Assessment Psychologists commonly draw on psychometric data (clinical test assessment data) and the diagnostic criteria outlined in the DSM-IV-TR. The DSM-IV-TR is the most widely used diagnostic classification system amongst mental health professionals. It’s chief limitation is that it relies on a categorical system of diagnosis, whilst this is widely recognized as a problem, there is no agreement on methods of dimensional classification, To this end authors such as Brown and Barlow have recommended that clinicians and researchers rely on a multi-trait/multi method model in developing a clinical diagnosis, hence the need for psychological test methods. The importance of following appropriate diagnostic and treatment evaluation guidelines is illustrated in the case of Tony Neindorf v Australian Country Choice Pty Ltd-PR972639 [2006] AIRC 344 (5 June 2006). In this case the Commissioner roundly criticized the treating psychologist commenting, “Mr Mellor’s evidence did not assist in this regard. Indeed Mr Mellors did not appear to have conducted any pain related questionnaire, but contended only that the disorder he diagnosed could come from pain.” There are a variety of measures of psychopathology, such as the Personality Assessment Inventory or the California Personality Inventory. However the Minnesota Multiphasic Personality Inventory - 2 (MMPI-2) has much stronger standing than any other equivalent test for personality and psychopathology; and several surveys of psychologists have pointed to the MMPI-2 being the most widely used measure. The MMPI was originally developed in the post world war 2 decade and is the widely used and best developed measure of personality pathology. The MMPI-2 was commissioned in 1982, and the revision was the first complete overhaul in the forty year history of this test. The University of Minnesota has an arrangement where a percentage of all sales are reinvested in developmental research. This has lead to the MMPI-2 being the most widely validated and psychometrically rigorous measure of psychopathology. Treatment The ACPTMH review refers to “exposure therapy” as the treatment of choice for anxiety and post traumatic stress disorders. Exposure therapy consists of pairing relaxation techniques with exposure to reminders of the original critical incident. The review recommends that exposure therapy be combined with cognitive behaviour therapy to obtain optimal results. Cognitive behaviour therapy consists of techniques designed to promote “evidence based or rational thinking” in combination with behavioural management skills. Personality and PTSD It is not clear as to the reason that some individuals do develop PTSD, while others do not. Exposure to traumatic events is not unusual. At least 50–65 per cent of community respondents report at least one traumatic event in their lives and yet a very small percentage of these respondents develop full blown PTSD. Creamer, Burgess and McFarlane reviewed data from a stratified sample of 10, 641 respondents taken from the Australian National Survey of Mental Health and Well-being. The estimated 12-month prevalence of PTSD was 1.33%; hence PTSD is less common than depression and anxiety disorders. It has been informally recognised since world war one, that previous trauma history affects personality resilience for coping with subsequent traumatic events. Williams (1999) nominates four points on how trauma may interact with personality structure. These are:
According to Williams, the exercise of trying to draw a distinction between chronic PTSD and personality change “is a nonsensical one. Changed personality could simply be seen as one of the many cognitive processes that would mitigate against the integration of trauma within the personality structure. It is not clear how the normal person would actually respond to the experience of a seriously life threatening situation.” There is also the difficulty of substituting objective realities with retrospective wisdom. It is not uncommon for highly symptomatic individuals to remain chronically traumatized; yet there is no evidence pre-morbid dysfunctionality. Cognitive models of PTSD have asserted that individuals with concrete black and white thinking styles or inadequate coping strategies or particularly rigid value systems are vulnerable to the development of post traumatic stress disorder. It is unclear as to how such propositions could be tested which makes them problematic in both a psychological and legal context. Williams provides an ironic comment to the effect that previous research on the contribution of premorbid personality found that “predictably increased scores for PTSD were linked with increased escape, avoidance, confrontational coping and to less support seeking and positive reappraisal. Escape avoidance, distancing accepting responsibility and confrontational styles accounted for 75% of coping strategies and were associated with avoidant personality styles” . Post Traumatic Stress Disorder and Malingering A related issue to validity, is the ability of a psychological test to detect malingered psychiatric symptoms. Again the MMPI-2 is the preferred test of choice. The MMPI-2 contains a set of subscales known as F scales, which are specifically designed to detect distortion on respondent’s test profiles. The F scales seem to perform particularly well in the detection of malingering, even under conditions of coaching. Meta-analyses have supported the ability and sensitivity of the MMPI-2 to detect malingering. In another study, participants were asked to complete the MMPI-2 and then asked participants to fake PTSD when completing the MMPI-2 on a second occasion. There were four conditions: a) uncoached b) coached about PTSD symptoms c) coaching about MMPI-2 clinical and content scales d) coaching about symptoms and validity scales. Participants in condition (d) were most successful in avoiding detection of malingered PTSD. However even in this condition, the F scales Family continued to have high positive and negative predictive power in detection of malingering. Authors of another study instructed one group of veterans who were seeking compensation for combat related PTSD to exaggerate symptoms. The other group were not provided with instructions to exaggerate. One particular F scale predicted 42% of the variance when differentiating between honest and exaggerating responders. As previously mentioned there are concerns that wide availability of PTSD criteria has made it easier to generate malingered claims. Estimates of malingering are extremely variable, as they range from 1% to 50%. The range of variation underlines the difficulties in proving that malingering has occurred if appropriate psychometric screening is not used. It is noteworthy that malingering often occurs in conjunction with antisocial tendencies. Resnick urges caution around a diagnosis of post traumatic stress disorder where the following indications are present:
Genuine PTSD sufferers will find it difficult to discuss the trauma experience without experiencing a high level of physiological arousal and anxiety. This type of discomfiture needs to be distinguished from the evasiveness of not being able to provide specific details about symptoms. Conclusions This paper has attempted to use a synthesis of case law and research to address six key challenges around the provision of expert evidence on post traumatic stress disorder. Two of these areas overlap with requirements in Section 79 of Evidence Act concerning the exception for expert evidence, to wit that admissibility of expert evidence is contingent on that expert having specialized knowledge or experience that can assist the court. It was suggested that there are a broad range of health professionals who can produce admissible evidence on mental health matters. A combination of large scale nomothetic surveys, evidence based best practice in treatment and assessment to individual clinical cases was suggested a resolution to the requirement that expert evidence be derived from scientific method. It was suggested that for a diagnosis of post traumatic stress disorder to be admissible that the factual basis of such an event needed to be established; and that the DSM-IV-TR critierion had formed a clinical framework of the type of event that could be accepted as traumatic. The issue of drawing a distinction between the contribution of premorbid personality and chronic post traumatic stress disorder remains problematic and difficult to test. It is fair to say that the solution to this issue is “a work in progress”. Psychometric assessment with the MMPI-2, as well as cross collaboration of factual evidence and a detailed clinical history covering contraindications of PTSD has been put forward as a strategy for the detection of malingered claims of PTSD. I Freckleton, Post Traumatic Stress Disorder: A challenge for public and private health law. 5 (1998) Journal of Law and Medicine p 252. American Psychiatric Association (2000) Diagnostic and Statistical Manual of Mental Disorders 4th Edition, American Psychiatric Association, Washington, D.C. p 463 Council of Australian Governments, National Action Plan on Mental Health 2006 – 2011 (2006) www.coag.gov.au/meetings/140706/docs/nap_mental_health.pdf C Slobogin, Pragmatic Forensic Psychology: A means of ‘scientising’ expert testimony from mental health professionals 9 (2003) Psychology, Public Policy, and Law, p 276 C Slobogin Pragmatic Forensic Psychology: A means of ‘scientising’ expert testimony from mental health professionals. 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