Investigative interviewing, dissociative identity disorder and the role of the Registered Intermediary

Brendan M. O’Mahony (CJS Psychology, Diss, UK)
Becky Milne (COFI, ICJS, Portsmouth University, Portsmouth, UK.)
Kevin Smith (Major Crime Investigative Support, National Crime Agency, London, UK)

The Journal of Forensic Practice

ISSN: 2050-8794

Publication date: 12 February 2018



Intermediaries facilitate communication with many types of vulnerable witnesses during police investigative interviews. The purpose of this paper is to find out how intermediaries engage in their role in cases where the vulnerable witness presents with one type of vulnerability, namely, dissociative identity disorder (DID).


In phase 1, data were obtained from the National Crime Agency Witness Intermediary Team (WIT) to ascertain the demand for intermediaries in DID cases in England and Wales within a three-year period. In phase 2 of this study four intermediaries who had worked with witnesses with DID completed an in-depth questionnaire detailing their experience.


Referrals for DID are currently incorporated within the category of personality disorder in the WIT database. Ten definite DID referrals and a possible additional ten cases were identified within this three-year period. Registered Intermediary participants reported having limited experience and limited specific training in dealing with DID prior to becoming a Registered Intermediary. Furthermore, intermediaries reported the many difficulties that they experienced with DID cases in terms of how best to manage the emotional personalities that may present.


This is the first published study where intermediaries have shared their experiences about DID cases. It highlights the complexities of obtaining a coherent account from such individuals in investigative interviews.



O’Mahony, B., Milne, B. and Smith, K. (2018), "Investigative interviewing, dissociative identity disorder and the role of the Registered Intermediary", The Journal of Forensic Practice, Vol. 20 No. 1, pp. 10-19.

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The role of the Registered Intermediary was one of the Special Measures introduced in England and Wales by the Youth Justice and Criminal Evidence Act 1999 (YJCE Act, 1999). The role emerged due to the volume of academic research that demonstrated that professionals across the criminal justice system asking questions to vulnerable persons were not as skilled at communication as they needed to be to elicit accurate information and to avoid miscommunication during the police interview or during cross-examination at court (Milne and Bull, 2001; Kebbell et al., 2000). Intermediaries, therefore, were introduced and are tasked with completing a full assessment of the communication needs of a vulnerable witness prior to interview and for court proceedings and subsequently facilitating communication between the vulnerable interviewee and the investigating officer or lawyer at court. The legislation enables an intermediary communication assessment to be completed in cases where the witness is: aged under 18, or has a mental disorder; has a learning disability; has a physical disability, or; has a physical disorder. Adult witnesses only fall within the scope of the legislation if the disorder or disability effects communication. It is the mental disorder limb of the legislation that is the focus of this research paper. The legislation in England and Wales separately defines “intimidated” witnesses as those whose quality of evidence is likely to be diminished as a result of fear or distress when testifying at court. Under the YJCE Act 1999, Registered Intermediaries are not available to intimidated witnesses unless they also meet the vulnerability criteria. Registered Intermediaries are trained professionals with backgrounds, such as psychology, mental health nursing and speech and language therapy (O’Mahony, 2009; O’Mahony et al., 2011). Intermediaries work solely within their expertise and, therefore, only those trained and skilled in mental health work would engage in mental health cases.

There is an emerging body of research examining the role of the intermediary which has included a case study approach examining interview transcripts where the vulnerable adult has a learning disability (O’Mahony, 2012). The views of defendant intermediaries working in the criminal courts have also been documented (O’Mahony et al., 2016). In addition, there has been research examining mock juror perceptions of the intermediary role in child witness cases (Ridley et al., 2015; Collins et al., 2017). Intermediaries are also available in other jurisdictions (see Cooper and Mattison, 2017, for an international comparison of three versions of the England and Wales intermediary model). However, there is a paucity of research internationally examining the intermediary function in cases where personality disorder or other mental health issues are the presenting condition in vulnerable witness interviews, although police officers’ perceptions and experiences with mentally disordered suspects has started to be examined (Oxburgh et al., 2016). Risan et al. (2016) have looked at how the interviewer should regulate and cope with distress during an investigative interview but the role of intermediaries was not examined in this context. Mental distress can lead to dissociation which can affect the investigative interview and there has been no published research examining how investigators identify and manage dissociation in police interviews.

Dissociation and dissociative identity disorder (DID)

The concept of dissociation has been described as a “woolly” area for many neurologists (Stone, 2006). Indeed, dissociation can be a normal part of human functioning but it can become unhealthy and maladaptive (Stone, 2006). Dissociation is described as occurring when “the individual deals with emotional conflict or internal or external stressors with a breakdown in the usually integrated functions of consciousness, memory, perception of self or the environment, or sensory/motor behaviour” (American Psychiatric Association, 2000, p. 811). Research has found that maladaptive dissociation is linked to traumatic events (van der Kolk et al., 1996). With this information in mind, it is essential to recognise that complainants in police interviews may experience dissociation when recalling traumatic events such as sexual abuse. There is a range of phenomena that are considered dissociative including amnesia for past events, depersonalisation (feeling disconnected from the body), derealisation (the sense that the environment is not real) and DID (Kennedy and Kennerley, 2013). Furthermore, investigative interviewers may be unaware that an interviewee is dissociating at times during the investigative interview when recalling traumatic events.

DID, also known as multiple personality disorder, is a complex dissociative disorder which is characterised by two or more distinct personality states (American Psychiatric Association, 2013). According to DSM-V, the disruption in identity involves a marked discontinuity in sense of self and sense of agency, accompanied by related alterations in affect, behaviour, consciousness, memory, perception, cognition and/or sensory-motor functioning.

When a client engages in therapy they may present with “alternate personalities” or “alters” (Positive Outcomes for Dissociative Survivors, 2015). These “alters” may or may not be aware of other “alters” within the system and the interviewer may notice a change in presentation from the interviewee in terms of age, gender or other characteristics. Watkins and Watkins (1997, pp. 65-6) theorise, from a psychodynamic perspective, how multiple personality “alters” originate. Using metaphor, they discuss how nations and large corporations cease to communicate and co-operate effectively with each other following extreme conflict. They hypothesise that, similarly, when some individuals have experienced severe threat, such as child abuse, splitting of the ego states occurs for reasons of survival. These ego states, which would normally co-operate to optimise effective living, are now re-established as “overt alters” developing “impermeable boundaries” where “intra-unit communication ceases or is greatly restricted”.

The theory of structural dissociation of the personality suggests that the personality of the individual with DID is divided among two or more subsystems or parts (van der Hart et al., 2010). The structural dissociation model examines a system in terms of the “Emotional Part” (EP) of the personality and the Apparently Normal Part (ANP) of the personality (van der Hart et al., 2010). The EP is strongly associated with memories of the trauma whereas the ANP is a part of the system that functions in daily routine and it is the ANP that may present to observers in the workplace or on initial contact with professionals. The EP may become apparent to the observer by a trigger to the trauma. The system of EPs and ANPs can become extremely complex according to the theory of secondary structural dissociation (more than one EP) or tertiary structural dissociation where there may be more than one EP and more than one ANP (van der Hart et al., 2010).

DID has been thought to be linked to a severe and prolonged history of childhood abuse (Sachs, 2015). In addition, the complexity and often contradictory nature of the accounts provided by complainants presenting with DID often creates suspicion as to the veracity of the allegations made (Sachs, 2015). Complainants with DID are considered by some to make unreliable witnesses and difficulties have been reported in how to interview them (Sachs, 2015). Whilst according to Sachs (2015, p. 73) clinicians and criminologists may often avoid interviewing persons with DID, she argues that such interviews are “necessary, possible and often quite therapeutic” and she offers guidelines for interviewers including consideration of the environment in which interviews take place, acknowledging that although you only see one person sitting opposite, you are interviewing a group and that it is necessary to listen to all communication rather than just the main person.

The concept of DID appears to be controversial (Dorahy et al., 2014) and a number of myths about the disorder remain (Brand et al., 2016). These myths include: a belief that DID is a fad; a belief that DID is primarily diagnosed in North America by DID experts who overdiagnose the disorder; a belief that DID is rare; a belief that DID is an iatrogenic, rather than a trauma-based, disorder; a belief that DID is the same entity as borderline personality disorder, and; a belief that DID treatment is harmful to patients (Brand et al., 2016). An alternative view is that DID is a disorder of self-understanding and that whilst trauma may play a role in dissociation, its role is not as central as others claim (Lynn et al., 2014). Indeed, it has been argued that there is a lack of strong empirical support for the claim that traumatic memories can be encoded without one being able to recall them in cases where dissociative amnesia is hypothesised (Lynn et al., 2014).

Whilst police interviewing officers in England and Wales are guided by the Achieving Best Evidence guidance (Ministry of Justice, 2011), there is currently no advice given to support investigators who are faced with a vulnerable interviewee presenting with DID. The Advocate’s Gateway (TAG) has published one “toolkit” to assist advocates to understand the complexities of questioning traumatised witnesses, “Working with Traumatised Witnesses, Defendants and Parties (2015)”. However, the guidance within the toolkit states:

The legal implications for giving evidence with this disorder (DID) are particularly complex. Can the person give evidence as one of their “alters” or only as their apparently normal personality? Expert advice should be sought

(p. 5).

Without guidance from the Achieving Best Evidence manual or from the TAG toolkit the investigating officer currently seeks advice from a Registered Intermediary as to the best method of communicating with a vulnerable witness with DID. To date there has been no published research in the UK as to the advice given by intermediaries and there appears to be an expectation that intermediaries have the requisite expertise to guide interviewing officers and lawyers at court as to the best way to communicate with these vulnerable witnesses. Three questions arise: How often do such cases occur? Do intermediaries have the requisite knowledge about such a complex condition? What do intermediaries advise? The exploratory research in this paper sought to address these questions.


In the first phase of this research, the Witness Intermediary Team (WIT) at the National Crime Agency (NCA) was contacted to establish the demand for Registered Intermediaries to assist police investigators in cases where the vulnerable witness had DID. Parameters were set to obtain data for the period January 2013 to January 2016 inclusive. The WIT was asked to search the database for requests made by the police where Dissociative Identity Disorder (DID), Multiple Personality Disorder (MPD) appeared on the police referral. The system in operation at the NCA at the time of requesting the data had a drop-down menu for police requests with the seemingly nearest option to select in cases of DID being personality disorder. This necessitated that the data for all cases where personality disorder had been selected to be interrogated in the free text to see if the various terms for DID were mentioned in the referral.

In the second phase of the research, an in-depth questionnaire was designed which included questions based on practitioner experience of authors 1 and 3 and the issues discussed in conversations with police officers who had previously sought advice about communicating with interviewees in DID cases. There were inherent difficulties with piloting the questionnaire due to the very small sample of prospective participants but the questionnaire was reviewed by the co-authors and by one intermediary practitioner in the workplace. Bristol Online software was utilised and a link to the questionnaire was made available on the intranet that all Registered Intermediaries have access to. The questionnaire (contact the first author for a copy of the questionnaire) consisted of 29 questions.

In addition to the participant demographics, the questionnaire sought information about the number of DID cases undertaken by each participant at police interview and at court; the formal and informal methods of assessment utilised; difficulties (if any) encountered during the communication assessment and/or interview; the advice about facilitating communication given to the interviewing officer and the court (if applicable); the type of interventions made during the police interview (and court, if applicable); previous specialised training and qualifications in DID undertaken by participants; the opinion of the participants about the qualifications and training that intermediaries should have to undertake DID cases; the opinion of the participants as to whether a mental health support worker might be more appropriate than an intermediary in DID cases. Finally, participants were given the opportunity to add “any other comments”.

It was apparent from the early stages of the research that there would be difficulties in identifying many participants who had engaged in the intermediary role in DID cases, due to the small number of intermediaries who have specialist mental health training in this area. (At the time of completing this research the number of intermediaries with specialist skills in DID has not been established by the authors as this information is not collated by the WIT at the NCA. DID cases are offered to intermediaries who have advised the Witness Intermediary Team Matching Service that they are skilled in working with personality disorders and/or other mental disorders). Seven Registered Intermediaries commenced the questionnaire but it was completed by only four participants. The professional backgrounds of the intermediaries who completed the questionnaire were social work (n=1), speech and language therapy (n=1), nursing (n=1) and psychology (n=1). There were two male and two female participants. The range of participant experience in terms of the number of intermediary cases of all vulnerability types undertaken was 5 to 500, with the average number of cases being approximately 200. The participant who had completed five cases was a relatively newly recruited intermediary (six months). The other participants had been Registered Intermediaries for 20 months, 8 years and 10 years.


The results are presented in two phases. In the first phase the details of the data obtained from the NCA is presented. It was found that the NCA does not currently list DID cases separately but includes these cases in the category of personality disorders. In the second phase, the data obtained from the in-depth questionnaire is presented. The results from the second phase of the research demonstrate that the work of the participants has been focussed almost entirely on the pre-interview communication assessment and the police interview. None of the cases referred to by the participants resulted in testimony being given by the interviewee at court. One participant reported having mentored a colleague who had one DID case at court.

Phase 1: How many DID cases?

The NCA identified 251 cases where personality disorder was on the referral for service form within the timeframe January 2013 to January 2016. These 251 cases included the cases where DID was a presenting vulnerability. The information from within the police referral form was examined to identify any reference made to DID or any related terms. Ten cases were identified (by the first author) and are listed in Table I. Two of these cases were unmatched to an intermediary meaning that no intermediary was available to accept the case within the prescribed time and location. An additional ten cases were identified where DID may have been a factor and are listed in Table II. Of these, a further two cases were unmatched and one referral was cancelled. The occupational backgrounds of the allocated intermediaries are documented in Tables I and II.

Phase 2: research questionnaire findings

One participant (P7) reported on the difficulties of arranging rapport building meetings and assessment meetings prior to the police interview as the interviewee often engaged and then disengaged from the process, before re-engaging again. In the same case the participant reported that the “fronting personality” of the interviewee presented initially as selective mute. One participant (P7) had written one court report but the defendant pleaded guilty and the complainant was not required to give evidence. However, in this case the intermediary had advised counsel how to communicate with the alters in the pre-trial process. Participants had no experience of facilitating communication during witness testimony at trial and so there is no information to report about this stage of the criminal justice process. The focus of information reported in the remainder of this section is on the police stage of the process, particularly on the advice given to the police following the intermediary communication assessment and the interventions made during the police interview. Previous training and experience together with perceived training needs for intermediaries accepting DID referrals is also reported in this section. Participants had limited experience of DID cases both prior to undertaking Registered Intermediary work (mean 1.5 cases; range 0-5 cases) and indeed in undertaking cases as an intermediary (mean 2.25 cases; range 1-3 cases).

Participants were asked what verbal or written advice, specifically related to managing Hosts (ANPs) and Alters (EPs), they had given to the interviewing officer prior to the police interview (Table III). Participants reported having focussed attention on the Host (ANP) to obtain the account and if an Alter (EP) was present, managing the situation by attempting to get the Host to return. One participant reported having had to contact the WIT advisor to gain advice as to whether evidence could be obtained from an Alter (EP). Another participant had to speak with senior officers and advisors. This highlights the lack of guidance that intermediaries have when undertaking DID cases. The answer provided by Participant 1 appears confusing; does s/he mean interviewing the Host (ANP) or does s/he mean interviewing the Host (ANP) and the presenting Alters (EPs) when s/he refers to the “whole person”? Seemingly, it appears to read that the Host is viewed as the “whole person” which leaves us wandering how the EP(s) may contribute.

Participants were asked about the interventions that they had used during police interviews and these are reported in Table IV. The results offer an insight into the differences in individual cases with one case being very complex to manage with child alters and another case requiring no intervention. Importantly, one participant reported that miscommunication can take place within the interview setting regardless of the presence of DID and intermediaries need to be mindful of the breath of communication issues that may occur. Additionally, as is often the case in intermediary work, comorbidities may exist such as anxiety, depression or intellectual disability although details of comorbidities (if any) were not collected in this research.

Intermediaries who have undertaken DID cases have limited specific training and qualifications in DID. They tend to have a more general background of working with cases where a broad range of mental health issues may present, for example, psychosis, mood disorders and personality disorders. It appears to be the case that participants were reliant on self-development through individually sourcing relevant training days, workshops and reading and research to develop their knowledge about DID. Data were not collected about whether the intermediaries who accept DID cases are registered with professional bodies such as the Health and Care Professions Council, and therefore accountable to professional bodies if found to be undertaking work outside of their skillset. Participants, nevertheless, hold the opinion that intermediaries engaging in DID cases do require specific training and qualifications, or at the very least, specific experience.

Finally, given the understanding that a witness with DID might present without additional communication difficulties, participants were asked if they thought that a mental health support worker might be more appropriate than a Registered Intermediary in DID cases. There was a mixed response to this question but, as highlighted by one participant, DID will always have some impact on communication.


There has been a substantial amount of psychological research about the appropriate questioning of children and persons with a learning disability and the research findings have led to best practice guidelines for police interviewing and for the questioning of witnesses at court, thus enabling equality of access to justice. There has been limited research on how mental disorder and mental distress impacts on effective investigative interviewing and questioning of witnesses at court. The dearth of DID cases apparently going to trial at court, as identified in part by this exploratory research, might suggest that persons with a DID diagnosis do not currently have equity of access to justice and indeed may be excluded from the justice system. The lack of guidelines to professionals on how to effectively question vulnerable witnesses with DID would certainly seem to indicate this inequality.

There were relatively few cases of DID referrals made by the police during the three-year period examined in this research. However, a minimum of ten cases were identified and the importance of managing these vulnerable witnesses within the criminal justice system so that their communication needs are met should not be underestimated. There were also another ten cases where DID may have been a factor but the information within the police referral is unclear. There is no psychiatric condition called “split personality disorder” and yet this terminology featured several times in the data. It is a term that is sometimes used to incorrectly refer to schizophrenia (McNally, 2007). Another issue to note is that it is not known how many cases of DID are not identified and yet may present in the police interview context. Some people who have been through integrative therapy may give the appearance that they are managing well in an interview but it is possible that, unknown to the interviewing officers, the interviewee is struggling with competing internal dialogue. Such dialogue is likely to interfere with concentration and listening skills. An emotional personality may be present which is directing the host not to talk to the police. If this seems an unlikely proposition to make it is perhaps not such a difficult step to recognise that many people narrating traumatic events within a police investigative interview, and indeed during cross-examination at court, may well be dissociating at times.

The authors have not located any published research that examines the prevalence of dissociation occurring within police interviews, in the absence of DID. Neither is there any published guidance to advise an interviewer how to identify signs of dissociation, and when identified, how to manage this within the interview. It is easy to see how dissociation within an investigative interview might be misinterpreted as vagueness, confusion which seemingly undermines credibility, or an opportunity to gain thinking time. For example, to change a false account. Dissociation may of course occur in child witnesses as well as adults and there is a gap in the evidence base as to the extent of this issue. More research is needed.

The four participants who completed the questionnaire and the other intermediaries accepting DID cases are groundbreakers in this complex role. It appears that without legal or professional advice they are attempting to provide a service as best as they can within their professional boundaries, although it is clear from their responses that they have limited experience with DID cases, not only in their role as intermediaries, but also in their previous work experience. One limitation of this study is that no participant had a background in occupational therapy and yet three cases were identified in Tables I and II where an occupational therapist had been allocated the referral. It is unclear why no psychologist or social worker is listed in Tables I or II as having accepted DID cases when one participant in this research identified themselves as having a background in psychology and one a background in social work. Case 208 might account for one of these but an alternative explanation is that the DID was not identified by the police at the initial referral stage but was subsequently identified. We do not know if the two intermediaries with speech and language therapy backgrounds plus additional training in art psychotherapy and anger management (who between them undertook 7 of the 20 cases identified in Tables I and II) are represented within this research. While the participants in this research do not fully represent the pool of intermediaries undertaking DID cases it does provide an insight into some of the difficulties experienced with such cases. In the experience of authors 1 and 3 of this paper, who are practitioners in the field of vulnerable witnesses, the issues raised by the four participants are highly relevant to developing best practice in England and Wales. Of concern is that 4 of the 20 cases identified in this research remained unmatched which indicates that there were not enough intermediaries with the appropriate specialism available within the timeframe and location required by the police.

Registered Intermediaries undertaking DID cases need evidence-based guidance and training to fulfil this role effectively. It is of some concern that, to a large extent, intermediaries are inviting officers to obtain accounts only from the Apparently Normal Personality (Host) to the exclusion of information from the emotional personalities (Alters). This may be a pragmatic approach to take and indeed it may be the method in which the legal profession prefers, but it seems to be entirely without an evidence base or without formal guidance from the prosecuting authorities. According to the structural dissociation model (van der Hart et al., 2010) the EPs (Alters) are strongly associated with memories of the trauma and it would seem that the interviewing officer would need to seek information from the EPs in order to obtain a complete account. It could be argued that an Apparently Normal Personality may not be aware of the existence of an emotional personality, and that the EP might have additional information not known to the ANP, which may assist the police investigation. If an interviewing officer gains information from only the ANP the court may need to be persuaded that a full account has been obtained.

One of the many challenges of working with DID cases is that we can never be sure how many EPs there are, the extent to which the ANP is aware of them, or the function that they serve. The effect of this is that we can never seemingly know which EPs might be able to contribute to the witness account and which EPs have the potential to obstruct the witness interview. Watkins and Watkins (1997) writing in the context of therapy, rather than investigative interviewing, observed that one of the most difficult tasks for the therapist is the management of malevolent alters. This task is seemingly magnified in the police interview context when trying to obtain a full evidential account and is indicative of the amount of time that will be required to establish rapport and trust with the interviewee and the consideration that will need to be given to the environment where the interview(s) is conducted.

The Advocate’s Gateway toolkit referred to earlier in this paper highlights the issue by questioning whether an “alter” can give evidence. It is unsatisfactory that the only guidance available within the toolkit is to seek expert advice when, given the knowledge that this is a controversial diagnosis, it is not clear where this advice should be sought from. One intermediary highlighted the point that other issues of miscommunication require intervention, as they might with other vulnerable witnesses, in addition to the extra needs of interviewees with DID. This begins to paint a picture of the complexity involved with these interviewees who may present with comorbidities such as impaired intellectual functioning, depression, anxiety and any other number of communication difficulties. It is for this reason, as identified by one participant that a Registered Intermediary may well be the preferred resource rather than a mental health practitioner who does not specialise in communication for courts.

The participants in this study reported that they have not generally had specialist training in assessing and meeting the communication needs of persons with DID. We argue that there should be a mandatory training course for intermediaries engaging in this work to ensure that each intermediary is operating to the same standards. Of course, the standards need to be identified first, in consultation with senior lawyers from the Crown Prosecution Service, academics and clinical professionals to identify the best way to manage interviews where the interviewee presents with emotional personalities. The authors are not aware of the attrition rate of DID cases as they progress through the criminal justice system and the collation of such data would be informative.

Implications for practice

  • The WIT may consider amending the way that data are stored on its database so that personality disorders and DID are not conflated. This should assist in only matching DID cases with Registered Intermediaries who specialise in this vulnerability.

  • The legal profession should provide guidance to the police as to what type of evidence is admissible at court. For example, can evidence be obtained during interview from the alters (Emotional Personalities) as well as from the host (Apparently Normal Personality). The academic literature on DID should be consulted before forming an opinion on this issue.

  • The findings of this study may assist intermediaries, interviewing officers and lawyers in gaining a better understanding of the complexity of DID.

  • There is a dearth of research about how dissociation is identified and managed in investigative interviews and at court. This needs to be examined to inform intermediary practice, police practice and courtroom questioning practice.

  • Research is required to examine how dissociation and DID may impact in suspect interviews and in defendant testimony at court and to identify appropriate safeguards.

Cases where dissociative identity disorder was identified from information within the police referral form

Case number Text in police referral Professional background of intermediary allocated the case as listed by the Witness Intermediary Team
1 Multiple personality disorder; dissociative personalities disorder; schizophrenia; bipolar affective disorder Occupational therapy
24 Personality disorders; self-harm; risk of suicide; 7 personalities; hallucinations and voices Speech and language therapy/art psychotherapy
30 Dissociative identity disorder Occupational therapy
34 Multiple Personality Disorder Speech and language therapy
37 Dissasociation (sic) identity disorder Speech and language therapy
91 7 personalities; hallucinations and voices Speech and language therapy/art psychotherapy
115 Multi personality disorder Speech and language therapy/anger management
166 Dissociative identity disorder Unmatcheda
208 DID (dissociative identity disorder) Data not recorded
215 Dissociative identity disorder Unmatcheda

Notes: Text as per the actual police request. aRegistered Intermediary not allocated to this case due to unavailability

Other possible cases of DID

Case number Text in police referral Professional background of intermediary allocated the case as listed by the Witness Intermediary Team
73 Personality disorder; disassociation disorder Speech and language therapy/anger management
82 Dissociative disorder Speech and language therapy/art psychotherapy
84 Dual personality disorder Speech and language therapy/anger management
87 PTSD; personality disorder; disassociation disorder; loses focus and attention Speech and language therapy/anger management
106 Split personality disorder Occupational therapy
140 Borderline split personality disorder Nursing
151 Split personality disorder Unmatcheda
171 Split personality disorder Speech and language therapy
178 Split personality disorder Unmatcheda
204 Disassociative disorder Referral cancelled

Notes: Text as per the actual police request. aRegistered Intermediary not allocated to this case due to unavailability

Advice given to interviewing officer following communication assessment

Participant number Advice given re-interviewing ANP & EP(s)
1 Still in discussions; advice given around interviewing the whole person rather than trying to interview each alter
3 Depending on the case: acknowledging X’s presencea; greeting that persona and then asking if Y could returnb (the base personality) to continue answering questions. Allowing for breaks whenever the RI needed to re-establish integration and the base personality’s presence/or to deal with the evident trauma or for the interviewing officer themselves to use agreed techniques to re-establish integration. Long discussions with senior officers and advisors in one case to try to establish a method of interviewing which would provide acceptable evidence. In each case the police had never heard of the disorder and needed much guidance to try to understand it
4 Discussed extensively with the WITc adviser. Decided that the witness could only give evidence when in ANP. When Alter was in control the evidence should be stopped
7 Gave advice via the fronting personality in terms of how best to communicate verbally and non-verbally. Also, gave advice on how best to manage the alters should they present based on my assessments and medical notes/input from psychsd, etc. In one case, it was appropriate to thank the alter should they present and ask for Xe to come back to continue with questioning; this was quite effective. Other advice includes making sure they address the alter in the correct way, recognising when/why the other alters may be presenting

Notes: aIt is the authors’ understanding that in this case “X” refers to an EP; bIt is the authors’ understanding that in this case “Y” refers to the ANP; cWitness Intermediary Team which is based at the National Crime Agency; dThis is assumed by the authors to refer to psychologists and/or psychiatrists; eIn this instance, the authors understand that X refers to the ANP

Interventions used during police interview

Participant number Interventions
1 Not applicable as interview has not taken place yet
3 Very frequent interventions in one case where one of the “child” alters became extremely traumatised and exhibited much disturbed child behaviour; another was extremely naughty-trying to tear things up/throwing/refusing to co-operate. It was almost impossible to re-integrate her and identify contact with her base personality to continue the interview
A second witness was able to stay in her base personality throughout the interview but needed frequent breaks “so the others could tell her what to say next”
4 None necessary
7 Very similar in terms of intervening should there be a miscommunication as in other vulnerable witness cases. Flagging up when another alter is presenting when the officer did not recognise it. Suggesting breaks to discuss communication issues with officer; assisting in managing the alter


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Further reading

The Advocate’s Gateway (2015), “Working with traumatised witnesses, defendants and parties (Toolkit 18)”, available at: (accessed 3 February 2017).


The corresponding author is a Registered Intermediary. Author 3 is employed as an advisor to the Registered Intermediary service.

Corresponding author

Brendan M. O’Mahony can be contacted at:

About the authors

Brendan M. O’Mahony is a Forensic Psychologist at CJS Psychology, Diss, UK.

Becky Milne is a Professor of Forensic Psychology at the COFI, ICJS, Portsmouth University, Portsmouth, UK.

Kevin Smith is a National Vulnerable Witness Adviser at the Major Crime Investigative Support, National Crime Agency, London, UK.