Medico-legal perspective on criminal responsibility in individuals with mental disorders

Abstract

Objectives

To analyze, from a medico-legal perspective, the relationship between mental disorders and criminal responsibility, identifying clinical-criminal patterns and judicial assessments in cases involving serious offenses.

Material and methods

A descriptive study was conducted, combining a specialized literature review with the analysis of judicial decisions. The study included rulings issued in Spain in which the presence of a clinically diagnosed mental disorder was recognized. Each case was examined in relation to the type of offense, psychiatric diagnosis, degree of criminal responsibility, and the penalty imposed.

Results

Psychotic disorders were more frequently associated with homicide, while personality disorders predominated in sexual offenses. Most defendants were deemed fully responsible, even in the presence of severe mental disorders. Semi-responsibility did not lead to a significant reduction in sentences, and psychiatric hospitalization was applied only in cases of non-responsibility. Although psychopathy could be identified in some clinical-criminal profiles, it did not appear as a formal diagnosis in any of the rulings.

Discussion

Findings reveal a restrictive application of mental disorder exemptions within the Spanish judicial system, consistent with the mixed (biological-psychological) model of criminal responsibility. Despite the recognition of psychopathology, ordinary imprisonment was prioritized over therapeutic measures. The results highlight the need for more specific diagnostic tools and adequate forensic and penitentiary resources to integrate both clinical and legal perspectives in the assessment of criminal responsibility.

Resumen

Objetivos

Analizar, desde una perspectiva médico-legal, la relación entre los trastornos mentales y la imputabilidad penal, identificando patrones clínico-delictivos y valoraciones judiciales en casos de delitos graves.

Material y método

Se realizó un estudio descriptivo, compuesto por una revisión bibliográfica especializada y un análisis de resoluciones judiciales. Se incluyeron resoluciones dictadas en España en las que se reconocía la existencia de un trastorno mental clínicamente diagnosticado y se realizó un análisis del tipo de delito, el diagnóstico psiquiátrico, el grado de imputabilidad penal y la pena impuesta.

Resultados

Los trastornos psicóticos fueron más frecuentes en delitos de homicidio, mientras que los trastornos de la personalidad predominaron en agresiones sexuales. La mayoría de los acusados fueron considerados plenamente imputables, incluso en presencia de trastornos mentales graves. La semiimputabilidad no supuso una reducción sustancial de las penas, y el internamiento psiquiátrico se aplicó únicamente en casos de inimputabilidad. La psicopatía, aunque identificable en algunos perfiles clínico-delictivos, no apareció como diagnóstico formal en ninguna resolución.

Discusión

Los hallazgos muestran una aplicación restrictiva de la eximente por trastorno mental en el sistema judicial español, en línea con el modelo mixto de valoración de la imputabilidad. A pesar del reconocimiento de psicopatología, la respuesta penal prioriza la prisión ordinaria sobre las medidas terapéuticas. Se evidencia la necesidad de herramientas diagnósticas más específicas y de recursos forenses y penitenciarios adecuados para integrar el enfoque clínico y jurídico en la evaluación de la responsabilidad penal.

Introduction

Historically, the relationship between mental illness and crime has always been a subject of debate. At the beginning of the 20th century, it was determined that some individuals who were classed as “major criminals” exhibited mental disorders that required therapeutic assistance rather than criminal punishment, although legal proceedings often ignored these conditions. Concepts such as “moral insanity” emerged to assess criminal responsibility, but their recognition was complex because individuals could maintain a facade of normality. Over time, the conceptual focus shifted from the dichotomy between criminal responsibility and irresponsibility to the notion of social dangerousness, which cantered on the likelihood of recidivism of criminal behaviour. This perspective sought to mitigate public and legal concerns that a psychiatric diagnosis would lessen the offender's criminal responsibility.¹

Although no single “criminal personality” exists, traits such as impulsivity and hostility are associated with criminal behaviour.² It is vital to understand that the existence of a clinical diagnosis does not, in itself, establish a causal relationship with criminal acts, and that most people with mental disorders are not violent. Various studies suggest that certain disorders (psychotic or personality disorders, especially antisocial and borderline) may increase the risk, although the relationship is neither linear nor deterministic.^1,3 In this context, psychopathology plays an essential role in determining criminal responsibility and assessing criminal dangerousness.^4,5 Despite advances, significant gaps remain, such as the need for a clear classification between psychopathy and antisocial personality disorder, and the scarcity of studies that analyse in detail the relationship between types of crimes and specific psychopathological categories.⁶

From a multifactorial perspective, psychopathology transcends its clinical definition to understand how certain patterns can influence criminal behaviour and criminal responsibility.⁷ For forensic assessment, it is essential to study those disorders that can affect a person's capacity to understand the unlawfulness of their actions or to act in accordance with that understanding. These are key elements of criminal responsibility.⁸ Internationally recognised diagnostic systems, such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the International Classification of Diseases (ICD-11), provide a rigorous basis for identifying and categorising mental disorders.^9,10 However, it is a fundamental premise that the presence of a formal diagnosis does not automatically imply an impairment of the person's volitional or cognitive capacity at the time of the crime.

The disorders most frequently associated with criminal behaviour are personality disorders (PDs) and psychotic disorders (PSDs). PDs, such as antisocial personality disorder, are characterised by persistent alterations in cognition, affect, and behavioural regulation, manifesting traits such as lack of remorse, impulsivity, and manipulation.^2,8 A concept closely linked to personality disorders is psychopathy, which is not included in clinical diagnostic manuals but is defined by callous affect, interpersonal exploitation, and an impulsive and irresponsible lifestyle. Psychopathy is associated with a high incidence of antisocial and violent acts and a strong relationship with recidivism.¹¹ Its rigorous assessment in forensic and research settings is carried out using specific standardised tools, notably Hare's Psychopathy Checklist-Revised (PCL-R).^4,5,12–14 On the other hand, psychotic disorders, such as schizophrenia, involve a profound alteration of mental functions and a significant break with reality. They manifest with positive symptoms (delusions, hallucinations) and negative symptoms (affective blunting, anhedonia). Criminal behaviour, in these cases, can occur during acute phases of the disorder, motivated by distorted perceptions and often without an apparent motive.^7,8 It is recognised, however, that criminality has a multifactorial origin, where personality acts as a modulating, not determining, factor, and the volitional component of the individual remains central.

Criminal imputability is the fundamental legal concept that determines a person's capacity to be held responsible for their actions, based on the preservation of their cognitive and volitional capacities. The system adopted by the Spanish Penal Code is the mixed or biological-psychological method, which requires the existence of a mental anomaly that has significantly affected the individual's capacity to understand the unlawfulness of their actions or to act in accordance with that understanding. Case law complements this model with qualitative criteria (nature of the impairment), quantitative criteria (degree of impairment), and chronological criteria (the duration of the impairment at the time of the act). In practice, the assessment is complex: personality disorders generally do not exempt individuals from responsibility, except in exceptional cases of severe impairment of will, while psychotic disorders, especially in acute phases, can lead to exemptions if a causal link between the symptoms and the crime is demonstrated.^8,15,16

The general objective of this study was to analyse the influence of mental disorders on the commission of serious crimes and on the assessment of criminal responsibility. Specifically, it aims to examine the main mental disorders present in individuals convicted of serious crimes, their relationship to the type of crime committed, and how the courts apply criminal responsibility based on the diagnosis and the degree of impairment of mental capacity at the time of the events. Based on these objectives, the study's main hypothesis is that the existence of a mental disorder does not, in itself, determine exemption from or reduction of criminal responsibility. Rather, this depends on the causal link between the mental disorder and the criminal behaviour, as well as on the judicial assessment of the degree of functional impairment of the individual. In short, the complexity of the relationship between mental disorder and criminality requires an individualised and multidisciplinary approach for a comprehensive understanding of the criminal phenomenon.

Material and methods

This is a descriptive study comprising two main components. First, a systematic search of scientific literature, specialised manuals, and academic articles was conducted. The databases consulted included PubMed, Scopus, Dialnet, and Google Scholar. The purpose of this review was to obtain an updated theoretical framework on the relationship between mental disorders and criminal behaviour, and the conceptualisation of criminal responsibility.

The second methodological pillar consisted of the analysis of a total of 38 criminal court rulings issued in Spain. These rulings, comprising judgements and court orders, were selected through a systematic search of the database of the Centre for Judicial Documentation (CENDOJ). The majority (26 of 38) were rulings from the Supreme Court, while 12 came from High Courts of Justice and Provincial Courts. Although the inclusion of rulings from different judicial bodies adds inherent variability to the study, it allowed us to confirm that the application of the mixed method and the restrictive trend in the recognition of mitigating circumstances are consistently maintained in the treatment of these serious crimes at the various judicial levels.

The inclusion criteria were strict: only rulings that expressly mentioned the existence of a relevant mental disorder were analysed, and this disorder had to have a recognised clinical diagnosis or be supported by medical reports. Cases in which the only factor mentioned was substance use were excluded from the analysis.

The 38 selected court rulings were equally divided into two categories of serious crimes: 19 cases of homicide or murder and 19 cases of sexual assault or abuse.

The choice of serious crimes was based on the fact that they allow for a more in-depth assessment of the application of crucial legal concepts such as criminal responsibility and mitigating or exculpatory circumstances due to mental impairment.

The key variables analysed in each court ruling focused on the degree of recognised criminal responsibility, classified as non-responsibility, partial responsibility, responsibility with mitigating circumstances, or full responsibility. These categories were differentiated according to the criteria of the Criminal Code and standard medico-legal practice: “non-responsible,” when the mental impairment completely nullified cognitive or volitional capacities; “partially responsible,” when there was a significant but not total impairment of these capacities, constituting an incomplete defence; “responsible with mitigating circumstances,” when the mental disorder did not affect responsibility but was considered as a mitigating circumstance in determining the sentence; and “fully responsible,” when no significant functional impairment was observed.¹⁷ In addition, the principal sentence imposed was analysed, distinguishing between ordinary imprisonment and security measures.

The information gathered from the court rulings was organised and analysed to identify patterns based on the type of mental disorder, the type of crime, and judicial assessments of criminal responsibility, thus enabling a structured and comparative approach to cases involving different mental illnesses. This methodological approach sought to provide a detailed understanding of how the Spanish judicial system addresses mental illness in the context of serious crimes and its legal consequences.

Results

General presentation of the analysed cases

This study is based on the analysis of 38 criminal court rulings issued in Spain, obtained through a systematic search of the CENDOJ database using the previously mentioned inclusion and exclusion criteria.

The selected rulings were evenly divided into two categories of serious offences: 19 rulings for homicide or murder and 19 rulings for sexual assault or abuse.

The key variables analysed in each ruling focused on the illness presented, the degree of criminal responsibility recognised, and the principal sentence imposed.

Overall, of the 38 rulings analysed, the distribution of the degree of criminal responsibility was as follows: 21 individuals (55.3%) were considered fully responsible; 11 individuals (28.9%) were classified as partially responsible; 4 individuals (10.5%) were considered responsible with mitigating circumstances; and 2 individuals (5.3%) were declared not criminally responsible.

A general summary of the cases analysed, including the type of offence, principal disorder, and degree of responsibility, can be found in Table 1.

Table 1.

General summary of cases analysed.

N°	Type of Offence	Principal Disorder	Criminal Responsibility	Sentence/Measure Imposed
1–19	Homicide/Attempted Homicide/murder	Mostly Schizophrenia and other Psychotic Disorders 1	10 Fully criminally responsible6 Partially responsible2 Not responsible1 Responsible with mitigation	Imprisonment, Psychiatric unit; Probation, Compensation
20–38	Sexual assault or abuse	Personality Disorders, Disabilities, Residual Schizophrenia	11 Fully criminally responsible5 Partially responsible3 Responsible with mitigation0 Not responsible	Imprisonment, Restraining Order, Probation, Disqualification, Compensation

Descriptive analysis by type of crime

The analysis of the 38 sentences revealed differential patterns between the two types of crimes in relation to the mental disorders involved and the forensic medical assessments issued.

Homicide or murder offences

In this group, which includes both completed homicides and attempted homicides and murders, the predominant diagnosis was psychotic disorder, present in 16 of the 19 cases (84.2%). The most frequent specific diagnoses were paranoid schizophrenia, delusional disorders, hebephrenic schizophrenia, and other psychoses. These cases were often characterised by active symptomatology or severe disorganisation at the time of the events.

The distribution of criminal responsibility for these offences was as follows: lack of criminal responsibility was recognised in 2 cases (10.5%), due to the total loss of cognitive and volitional capacities, generally in the context of an acute psychotic episode; partial criminal responsibility was considered in 5 judgements (26.3%), indicating a significant impairment of faculties without total exemption from responsibility. In one case (5.3%), mitigating circumstances were recognised, corresponding to a mild disorder without full impact; and in 10 cases (52.6%), the defendants were determined to be fully responsible, either because the disorder was in a residual phase or because no relevant functional impairment was proven at the time of the events.

The sentences imposed in cases of non-responsibility resulted in psychiatric confinement, with durations between 8 and 19 years, usually accompanied by subsequent supervised release and compensation. For those deemed partially and fully responsible, ordinary prison sentences were imposed, ranging from 4 to 20 years, in addition to the corresponding complementary measures such as probation, restraining orders prohibiting contact with the victims, and compensation obligations.

Sexual assault and abuse

In the second group, the 19 cases analysed included sexual assaults with or without penetration, repeated sexual abuse (mostly against minors), and aggravated sexual violence. Unlike homicides, personality disorders predominated in these offences, present in 14 of the 19 cases (73.7%). The most frequent diagnoses were antisocial, narcissistic, or mixed personality disorders, often accompanied by affective dysfunctions or cognitive impairment. Other cases included mild intellectual disabilities, stabilised psychotic disorders, or functional diagnoses without a structural basis.

Criminal responsibility in this group was distributed as follows: 11 defendants (57.9%) were considered fully responsible, as no significant impairment of their mental faculties was found. In 5 cases (26.3%), partial responsibility was recognised due to mild or moderate impairments that partially affected impulse control or judgement. Three sentences (15.8%) reflected a mitigating circumstance of criminal responsibility, where the mental impairment was deemed insufficient to modify criminal responsibility but relevant for sentencing purposes. No cases of lack of criminal responsibility were recorded in this group.

In all cases of sexual assault or abuse, prison sentences were imposed, with an average duration of between 6 and 15 years. These sentences were systematically accompanied by ancillary measures, such as a restraining order prohibiting contact with the victim, disqualification from exercising parental rights or working with minors, supervised release, and, in some cases, the obligation to undergo psychiatric treatment while in prison, in addition to civil damages.

Fig. 1 shows the distribution of mental disorders by type of crime, while Fig. 2 illustrates the distribution of criminal responsibility according to the type of crime.

Figure 1.

Distribution of mental disorders by type of crime.

Figure 2.

Distribution of responsibility by type of crime.

Descriptive analysis by type of disorder

The classification of mental disorders diagnosed in the 38 sentences was grouped into 3 categories: psychotic disorders, personality disorders, and other diagnoses.

Psychotic disorders

This group represented the largest number, with 20 cases (52.6% of the total). The most frequent diagnoses were paranoid schizophrenia, hebephrenic schizophrenia, delusional disorders, schizoaffective disorder, and various forms of unspecified psychosis. These disorders appeared mainly in homicide cases and were characterised by active symptoms or severe disorganisation at the time of the events.

Criminal responsibility in cases with psychotic disorders was distributed as follows: 11 defendants (55%) were considered fully responsible; 6 defendants (30%) were assessed as partially responsible; 2 people (10%) were declared not responsible, with total annulment of their mental faculties; one case (5%) was deemed criminally responsible with mitigating circumstances due to mild impairment, without full repercussion.

The measures adopted in this group ranged from long-term psychiatric hospitalisations to ordinary prison sentences, with or without additional measures.

Personality disorders

This group included 12 sentences (31.6%), mostly related to sexual assault offences. The predominant diagnoses were antisocial personality disorder; mixed personality disorder; narcissistic personality disorder; borderline personality disorder; and dependent personality disorder, frequently accompanied by high impulsivity, poor emotional control, or mild cognitive deficits.

Criminal responsibility in this group was as follows: 7 individuals (58.3%) were declared fully criminally responsible; 2 individuals (16.7%) were deemed partially criminally responsible; 3 cases (25%) received a finding of criminal responsibility with mitigating circumstances due to non-disabling mental impairment.

In all cases of personality disorders, ordinary prison sentences were imposed, accompanied by ancillary measures such as probation, specific disqualifications, and, in some cases, psychiatric treatment while in prison.

Other diagnoses

The third group comprised 6 cases (15.8%), with diverse diagnoses such as mild intellectual disability, affective disorders, impulse control disorders, or adjustment disorders. These conditions were more functional in nature, generally stable, and had less overall impact on mental capacities.

In this group, the following criteria were used to determine criminal responsibility: 3 individuals (50%) were considered fully responsible, and 3 individuals (50%) were considered partially responsible.

No cases of non-responsibility or mitigation of punishment due to mild disorder were recorded in this group.

The rulings for these diagnoses tended to recognise some functional impairment without deeming the individuals non-responsible, imposing prison sentences with complementary measures and without requiring psychiatric hospitalisation.

Fig. 3 illustrates the distribution of criminal responsibility by type of disorder, while Fig. 4 shows the percentage of criminal responsibility by type of disorder.

Figure 3.

Distribution of criminal responsibility by type of disorder.

Figure 4.

Percentage of criminal responsibility by type of disorder.

Discussion

The comprehensive analysis of 38 court rulings, encompassing serious crimes such as homicide and sexual assault, offers a detailed perspective on the complex interplay between mental disorders and criminal responsibility within the judicial system. A central and recurring finding is that, despite the recognition of a relevant mental disorder in the accused, the diagnosis alone does not automatically imply impaired criminal responsibility. Case law requires that the mental impairment actually and significantly affect the accused's cognitive and volitional capacities at the time of the crime in order to consider an exemption or mitigating circumstance. This restrictive application is consistent with the mixed or biological-psychological approach adopted by the current Spanish Penal Code. The study confirms this application, as the majority of the accused (21 out of 38 cases, 55.3%), despite having a recognised mental disorder, were deemed fully responsible. This assessment requires the simultaneous consideration of qualitative criteria (nature of the impairment), quantitative criteria (degree of impairment), and chronological criteria (the timing of the impairment at the time of the act).

The study reveals a clear distinction between the type of disorder diagnosed and the nature of the crime committed, establishing distinct clinical-criminal patterns. In homicide or murder cases, psychotic disorders, such as paranoid schizophrenia and its variants, were the predominant diagnoses (16 of 19 homicide cases; 84.2%). These cases often occur during acute phases of these disorders, motivated by distorted perceptions of reality, without an apparent motive, and with little awareness of the unlawfulness of the act. In contrast, in cases of sexual assault or abuse, personality disorders (14 of 19 sexual assault cases; 73.7%), such as antisocial and narcissistic personality disorders, were the most frequent, along with mild intellectual disability. These profiles are linked to more planned, recidivist, and manipulative behaviours, characterised by emotional coldness, low empathy, and disregard for the victim's rights. These patterns coincide with those found in the reviewed literature.^2,8,12 The association between the type of disorder and the type of crime reinforces the need to consider clinical diagnosis as a fundamental tool for understanding the criminal act.

Regarding the determination of criminal responsibility, the study confirms that the existence of a diagnosed mental disorder does not automatically imply an exemption or reduction of responsibility. Spanish jurisprudence applies the mixed model, which requires a real and concrete impairment of cognitive and volitional capacities at the time of the events. Of the 38 cases analysed, the largest group consisted of those fully responsible for their actions (21 cases; 55.3%), followed by those partially responsible (11 cases; 28.9%), those responsible with mitigating circumstances (4 cases; 10.5%), and only 2 cases of non-responsibility (5.3%). The study supports the hypothesis that criminal responsibility depends on the causal link and the functional impairment of the individual, not solely on the diagnosis. The high rate of full responsibility (55.3%) suggests consistent functioning of the system during the judicial assessment phase, as it is coherent with the restrictive application of the mixed method.

When analysing criminal responsibility according to the type of disorder, it is observed that psychotic disorders are most frequently associated with situations of non-imputability (2 out of 20 cases; 10%) or partial imputability (6 out of 20 cases; 30%). However, even in the presence of psychosis, a significant number of defendants (11 out of 20 cases; 55%) were considered fully responsible, especially when the clinical picture was stable, and no direct functional impairment could be proven at the time of the crime. Furthermore, personality disorders were mainly linked to rulings of full imputability (7 out of 12 cases; 58.3%), with partial imputability (2 out of 12 cases; 16.7%) or imputability with mitigating circumstances (3 out of 12 cases; 25%) being less common. This reinforces the medico-legal doctrine that personality disorders, on their own, do not usually justify the application of exemptions, except when accompanied by alterations that clearly affect the capacity for understanding or volition.^8,15

Regarding the sentences imposed, it is observed that, with the exception of the two cases of diminished responsibility (where psychiatric confinement was applied), the primary sentence was ordinary imprisonment. This general tendency to impose ordinary prison sentences, even for the 11 cases of partial responsibility, suggests a clear prioritisation of the punitive approach.^4,5,7

The present study argues that the limitations of the penal system lie not only in the restrictive judicial assessment of criminal responsibility but also, crucially, in the sentence execution phase. Although in more than half of the cases involving criminal responsibility (20 of 36 cases; 55.6%), the generic indication for psychiatric treatment was included, its practical application is seriously limited by the scarcity of specialised resources in the prison system. This situation underscores structural deficiencies that negatively impact the clinical evolution of offenders and the prevention of recidivism, forcing us to reflect on the actual suitability of the prison environment to care for these profiles.^18,19

A notable observation is the scant explicit mention of psychopathy as a diagnosis in the court rulings. Although many defendants, especially in sexual offences linked to personality disorders, exhibited traits consistent with this profile (lack of empathy, manipulative behaviour, recidivism, or criminal planning), this term does not appear as a formal diagnosis in any of the rulings. This absence can be explained by several reasons. First, psychopathy is not recognised as an independent diagnostic category, nor does it constitute a graded category superior to antisocial personality disorder in the classification systems used, such as the DSM-5 or the ICD-11. Furthermore, its low prevalence in the general population, estimated at around 1%, could contribute to its infrequent formal diagnosis, even in forensic contexts, since only a small number of individuals meet the full established psychopathic criteria.¹¹ Additionally, its rigorous identification requires the application of specific structured and standardised tools, such as Hare's PCL-R.¹⁴ This study suggests that the under-detection of this profile appears to be due to prevalence, structural, and procedural reasons, as the application of such comprehensive assessments is not always feasible, whether due to time constraints, limited technical resources, or the prioritisation of formal categorical diagnoses. Finally, in the Spanish judicial system, the diagnosis of antisocial personality disorder tends to be used as a practical equivalent, even though the terms are not synonymous. This omission has significant implications, as psychopathy has a strong association with violence and recidivism, and its under-detection limits the specificity of criminological risk assessment.^12,13

To conclude, this study analysed how the presence of mental illness in the commission of serious crimes is addressed judicially in Spain. It highlights that the diagnosis of a mental disorder does not automatically imply an impairment of criminal responsibility; a real and demonstrable alteration of the individual's cognitive or volitional capacities at the time of the crime is required. Distinct clinical-criminal patterns were observed, with psychotic disorders predominating in homicide cases and personality disorders more frequent in sexual assaults. The absence of psychopathy as a formal diagnosis in the sentences is notable, limiting the information relevant to assessing this condition. Ultimately, although psychopathology is recognised in legal proceedings, the complexity of the relationship between mental disorder and criminality, coupled with social stigma, demands an individualised and multidisciplinary approach that integrates medical, psychosocial, and legal criteria to tailor the judicial response to the clinical, personal, and social characteristics of the accused. Moving beyond reductionist explanations focused solely on psychopathological disorders is crucial for a comprehensive understanding of the criminal phenomenon.

Funding

The author declares that this research did not receive any specific grant from agencies in the public, commercial, or non-profit sectors.

Declaration of the use of artificial intelligence

The author declares that NotebookLM was used as a support tool for writing and linguistic revision tasks during the preparation of this manuscript. The content has been reviewed and validated in its entirety by the author, who assumes full responsibility for the final text.