¹Institute of Psychiatry- Federal University of Rio de Janeiro-Brazil. Fluminense Federal University- Niteroi-Rio de Janeiro-Brazil
²Hospital das Clínicas. Federal University of Pernambuco-Brazil
³Universidade de Pernambuco- Brazil
⁴Instituto de Medicina Social e Criminologia. São Paulo-Brazil
⁵Federal University of São Paulo-UNIFESP- Brazil
⁶Faculdade Paulista de Ciências da Saúde-Brazil
⁷Federal University of Rio Grande do Sul. HCPA- Brazil

*Address for Correspondence:Alexandre Martins Valença , Institute of Psychiatry- Federal University of Rio de Janeiro-Brazil. Fluminense Federal University- Niteroi-Rio de Janeiro-Brazil. E-mail Id: avalen@uol.com.br

Submission: 20 April, 2026 Accepted: 12 May, 2026 Published: 14 May, 2026

Copyright: © 2026 Valença AM, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Keywords:Delusional disorder; Criminal responsibility; Forensic psychiatry; Criminal imputability; Psychosis; Homicide

The assessment of criminal responsibility in individuals with mental disorders represents a critical intersection between psychiatry and law. In Brazil, the biopsychological criterion is applied to determine criminal imputability, requiring both the presence of a mental disorder and its impact on the individual’s capacity for understanding and self-determination. This study analyzes the application of this criterion through a forensic psychiatric case involving a 42-year-old male diagnosed with delusional disorder who committed homicide motivated by religious delusions. A clinical-forensic evaluation was conducted, focusing on four key elements: identification of mental illness, establishment of a causal nexus, assessment of cognitive capacity to understand the illicit nature of the act, and evaluation of volitional capacity. Although the individual demonstrated formal awareness of the illegality of the act, his behavior was significantly influenced by a structured delusional system, impairing both judgment and self-determination. Based on these findings, the subject was considered criminally non-imputable and subjected to a security measure involving psychiatric hospitalization. The case highlights the importance of rigorous forensic psychiatric evaluation and reinforces the relevance of the biopsychological model in ensuring fair judicial decisions. Additionally, recent literature on delusional disorder and violent behavior supports the findings, emphasizing the role of delusional content in shaping criminal actions.

Criminal imputability is an essential element of criminal law, as it defines the possibility of holding an individual criminally responsible for their actions. In Brazil, the biopsychological criterion is adopted, according to which criminal responsibility depends not only on the presence of a mental disorder, but also on proof that this disorder impaired the individual’s capacity to understand the illicit nature of the act or to self-determine behavior [1]. In this context, forensic psychiatry plays a fundamental role by integrating medical and legal knowledge, assisting the justice system in assessing Criminal responsibility [2]. Studies have expanded the understanding of the relationship between mental disorders and violent behavior, including the analysis of homicidal ideation in clinicat contextes [3]. The biopsychological criterion requires a combined analysis of biological and psychological factors, making it necessary to demonstrate that the mental disorder directly influenced the individual’s conduct [4]. Contemporary research indicates that psychotic disorders are associated with a higher risk of violent behavior in certain contexts [5]. Recent studies show that homicidal ideation may be associated with specific psychopathological conditions and is more frequent in individuals with severe mental disorders [6]. Furthermore, investigations indicate that homicide offenders with psychotic disorders present distinct clinical patterns, often related to structured delusions [7].

Delusional disorder, classified as F22 in the ICD-10 [8], is characterized by persistent false beliefs. According to the DSM-5 [9] of the American Psychiatric Association, delusional disorder is a psychotic disorder marked by the presence of one or more persistent delusions lasting at least one month, without marked impairment of overall functioning and without the typical symptoms of other psychotic disorders such as schizophrenia. Delusions are false beliefs firmly held despite contrary evidence and may be plausible or implausible. The DSM-5 [9] classifies delusional disorder into different subtypes according to the predominant theme : erotomanic type (belief that another person is in love with the individual), grandiose type (convictions of great worth, power, or special identity), jealous type (delusion of partner infidelity), persecutory type (belief of being persecuted or conspired against), somatic type (concerns about bodily functions or health), mixed type (no single predominant theme), and unspecified type. These subtypes are clinically and forensically relevant, as the content of delusions may directly influence behavior, including the possibility of aggressive conduct in certain cases. Such delusions may directly affect behavior, particularly when they involve persecutory or mission-oriented content [7].

The analyzed case refers to a 42-year-old Brazilian male with a high school education and technical training in aircraft mechanics. The individual was under judicial custody after murdering his ex-wife in 2008.
This is a forensic psychiatric case report. The examination aimed to evaluate the patient’s capacity for understanding and self determination, determine his level of criminal responsibility in relation to the offense committed, and apply the biopsychological criterion of criminal imputability.

Two interviews were carried out, each lasting approximately two hours, at the Instituto de Perícias Heitor Carrilho, an institution responsible for criminal forensic evaluations in the state of Rio de Janeiro, Brazil. The patient’s niece participated in one interview and reported that the patient had no prior history of aggressive behavior before the homicide. She noted that the patient appeared more irritable in the days preceding the crime. The patient had no previous history of alcohol or psychoactive substance use, and there was no family history of mental illness. The standardized tool used was the PANS scale (10) yielding a score of 20 ± 8.
According to case records, the crime was motivated by conflicts related to religious delusions. The patient presented a structured delusional system, in which he believed he had been chosen by a divine entity to fulfill a specific mission: to apply punishments, including death, to individuals who violated certain religious precepts. Reports indicate that the individual developed delusional ideas years before the crime, including the perception of receiving subliminal messages and the conviction that he had a special mission. In the period preceding the homicide, persecutory and punitive thoughts intensified, directed at members of his religious community, including his wife.
On the day of the crime, following an argument motivated by religious disagreement, the individual killed the victim with multiple stab wounds. Subsequently, he did not attempt to conceal the crime and, after a few days, voluntarily presented himself to the police, confessing the act and leading officers to the location of the body. During forensic evaluation, delusional disorder (ICD-10 F22) was diagnosed, characterized by systematized delusions with mystical and persecutory content.

In forensic evaluation, the first step consists of identifying the mental disorder [4]. In this case, delusional disorder was classified as a mental illness relevant to criminal law. The second step involves establishing the causal nexus between the disorder and the crime. Evidence indicates that, in cases of psychosis, violence is often related to the content of delusions. The third step refers to the capacity to understand the illicit nature of the act. Although the individual may formally recognize the illegality of the act, his interpretation may be distorted by delusional beliefs. The fourth step consists of evaluating self-determination.
Studies show that individuals with psychotic disorders may present significant impairment in volitional capacity [11]. In addition, research indicates that individuals considered non-imputable due to mental disorders exhibit clinical patterns consistent with those observed in this case [7]. The literature also indicates that homicidal ideation may evolve into violent behavior in specific contexts [6]. Additional clinical and social factors, such as psychiatric history and context of radicalization, may also influence violent behavior in individuals with mental disorders [12].

The relationship between delusional disorder and violent behavior—especially homicide—is complex and cannot be reduced to a single explanation. Most patients with psychotic disorders are not violent; however, there is a subgroup in which certain factors significantly increase the risk. One of the central elements is the content of the delusion: persecutory delusions (ideas of being persecuted, threatened, or betrayed) and religious delusions [13] that are not being respected, as in the present case, are more frequently associated with aggression. In such situations, the patient may interpret others as a real threat and act in a “defensive” manner, even though this is based on a distorted perception of reality. Strong delusional conviction, lack of insight, and intense emotional states (such as fear and anger) further increase this risk.

However, delusional content alone does not explain why some individuals become violent while others do not. Additional factors are decisive, including a prior history of violence, substance use (especially alcohol and stimulants), social isolation, acute stress, and lack of adequate treatment. It is possible that, if the patient in question had received psychiatric treatment, the crime might not have occurred, as the treatment could have mitigated the delusional manifestations. On the other hand, it is well established that protective factors include regular follow-up, family support, psychosocial interventions, and appropriate symptom management. Therefore, the risk of violence in patients with delusional disorder should be understood as the result of a multifactorial interaction, rather than an inevitable consequence of the illness—an understanding that is essential to avoid stigmatization and to guide effective prevention strategies.

The analyzed case demonstrates the importance of correctly applying the biopsychological criterion in the assessment of criminal imputability. The decision of non-imputability and the application of a security measure are supported by both classical and contemporary literature, highlighting the need for an integrated approach between psychiatry and law.
Current mental health policies and clinical practices have failed to recognize that aggressive behavior and victimization are significant issues for many patients with severe mental disorders. Consequently, healthcare services have not provided sufficient resources to address these problems, increasing the number of patients transferred to forensic services. The study of motivating factors for violent behavior may provide insights for the development of therapeutic interventions in individuals with psychotic disorders at risk of violent conduct.

Valença AM, Dourado Junior JB, de França MF, Rigonatti LF, Cordeiro Q, et al. Delusional Disorder and Crime: A Forensic Case Study. J Forensic Investigation. 2026; 13(1): 1.