In detail

Psychological expert: introduction and process

Psychological expert: introduction and process

In this article we will see one of the most systematic proposals made to guide the practice psychological expert formulated by Blau (1984). This author distinguishes 6 stages in the realization of the expert opinion:

  1. Case Initiation
  2. File Preparation
  3. Data Collect
  4. Needs assessment
  5. Strategy Selection
  6. Report itself

Next we will see each of these stages.


  • 1 1. Initiation of the case
  • 2 2. Preparation of the file
  • 3 3. Data collection during the psychological expert
  • 4 4. Needs assessment
  • 5 5. Selection of strategies for the psychological expert
  • 6 6. The expert report itself

1. Initiation of the case

The beginning of a survey starts from a first contact between the lawyer and the psychologist. On some occasions it is the client himself who takes the initiative, although this does not mean that the interview between his lawyer and the psychologist is subsequently carried out.

Similarly, The expert can be appointed directly by the judge. Either in the exercise of its faculty of free designation, or by lottery among those listed in a proposal provided by the Official College of Psychologists (the official list).

The first contact with the lawyer is of great importance since it will derive main elements of the frame of reference of the performance of the expert.

In this interview the following information will be collected

The facts of the case

That is, the main facts of the case and for which the expert intervention is requested psychological (extract of the summary or an advance of this). Based on them, the forensic psychologist you must decide if it belongs to you exclusive or not the expert intervention.

The probable date of the hearing hearing

Since the psychologist will need evaluate if you have the time to properly perform their work. It must be borne in mind that in every examination it is necessary:

  • Perform a brief review of the research literature related to the case studies
  • Perform a scan on the subject
  • Prepare the opinion

The hypothetical questions to which the psychologist will have to answer as Expert

This aspect is crucial since the expert activity must turn on them and those that will have to be limited in the opinion.

The characteristics and availability of the complainant

For example, Are subjects to explore accessible? The characteristics of the contexts in which the explorations will be carried out Do they have the minimum adequacy? This will allow us to properly perform the explorations or advise giving them up.

Request for other reports

For example, if available and relevant use of previous medical, school, work or psychological reports… If other expert opinions have been made.

The fee agreement to conduct the psychological expert

An estimate of the expert's fees must be offered based on the expected complexity of your intervention. It is highly advisable to establish a provision of funds between 40 and 60%.

2. Preparation of the file

The complexity that the psychological expert He advises paying attention to the material organization of the file. The content that will usually have an expert file will be the following:

  • Valuations derived from each of the psychological tests used in an opinion appropriate to the hypothetical questions
  • Initial documents: data sheet, summary summary, correspondence of the plaintiff lawyer, etc.
  • Other reports on the subject issued by other instances or experts
  • Notes taken in the course of the interviews with the subject, the lawyer or the judge
  • Case Chronology
  • Fee Registration Sheet
  • Various matters

To facilitate the management of the file, it is convenient for the psychologist to create the previous forms to meet the exposed needs.

3. Data collection during the psychological expert

In the expert investigation it is necessary to use all available methodological resources to give an adequate answer to the hypothetical questions.

The possibility and usefulness of complex scans, either for its duration, cost, sophistication of the methods used that are often rejected in clinical examinations for practical reasons, etc.

Data collection must be oriented to meet the needs of the questions, but not strictly limited to these among other things because sometimes the forensic psychologist will have to answer unanticipated questions or elements of detail.

To choose the evaluation methods and techniques, the psychologist will adjust to the level of knowledge and research available on the study problem, taking into account the necessary scientific justifications about the validity and reliability of the evaluation instruments used, the validity and capacity Explanatory of the categories and terms used in the report.

Likewise, must conform to the scientific process of elaboration, discussion and integration of hypotheses, being able to refer to any of the scientifically recognized psychodiagnostic models.

4. Needs assessment

At this time, The forensic psychologist evaluates whether or not the data collected is adapted to the needs that pose the hypothetical questions and, consequently, formulate whether new exploration objectives proceed or justify that it cannot be addressed.

5. Selection of strategies for the psychological expert

It is neither possible nor advisable to propose a standard model for expert examinations of the type of use of batteries constituted by certain evaluation techniques applicable regardless of the characteristics of the specific case.

Therefore, it is not about opting for exploration models for each class of demand (for example, competition, imputability, danger, custody ...) but a true discussion and methodological design must be made before each intervention object.

Other types of strategies are those related to the peculiar dynamics of hearing hearings when the direct testimony of the expert is required. It is very useful to have a reference book on various aspects that may be asked in the views:

For example, validity and reliability and scientific support of the procedures used, the control that has been carried out on the phenomena of simulation and falsification of declarations, data on statistical indexes, etc.

6. The expert report itself

The expert would have to present his opinions in writing and, sometimes, this will be all your intervention. Written psychological reports raise numerous problems that are exacerbated in the case of judicial practices.

Diagnostic tasks can be experienced by the professional with some fear for the legal and ethical responsibility they entail. As Weiner points out, The psychologist can think what he wants, but he should only write what he is prepared to testify in court.

To avoid undesirable effects, Every psychological expert must be guided by the following guidelines:

  • The content will be adapted to the basic aspects of the case: introduction, procedures used, conclusions and discussion
  • Clearly express everything relevant to the case avoiding dark or ambiguous terms
  • It will exclude or relativize everything that is not justified in an objective way detailing the confidence levels of the predictions
  • It will conclude with one or more opinions that the expert gives in response to the questions hypothetical that were formulated by the judge or lawyers


  • Blau, T. (1984). The Psychologist as Expert Witness. John Wiley and Sons. New York
  • Echeburúa, E., Muñoz, J. M., & Loinaz, I. (2011). Forensic psychological evaluation versus clinical evaluation: proposals and future challenges. International Journal of Clinical and Health Psychology, 11(1), 141-159.
  • Muñoz, J. M. (2013). The forensic psychological evaluation of the psychic damage: proposal of a protocol of expert performance. Yearbook of legal psychology, 23, 61-69.