Pre-Law: Psychology and the Law

Case 1: M'Naghten's Case (1843)—The Insanity Defense

Summary:
In 1843, Daniel M'Naghten was charged with murder after killing Edward Drummond, the secretary to the British Prime Minister. M'Naghten claimed that he was suffering from delusions, believing that Drummond was conspiring against him. He stated that he did not understand the nature of his actions because of his mental illness. During the trial, medical experts testified that M'Naghten was unable to comprehend the wrongfulness of his actions due to his delusions. The court ruled that M'Naghten was not criminally responsible for his actions, as he lacked the mental capacity to understand the consequences of his behavior.

Legal Impact:
This case established the M'Naghten Rule, which serves as a standard for the insanity defense in many legal systems today. According to the M'Naghten Rule, a defendant can be excused from criminal liability if, due to mental illness, they were unable to understand the nature of their actions or the wrongfulness of their conduct at the time the crime was committed. This ruling shaped how courts evaluate the mental state of defendants claiming insanity in criminal cases.

Case 2: Tarasoff v. Regents of the University of California (1976) – Duty to Warn

Summary:
In the 1970s, a University of California student, Prosenjit Poddar, confided to his therapist that he intended to kill a woman named Tatiana Tarasoff. Despite the student’s threats, the therapist did not inform Tarasoff or take steps to warn her of the danger. Later, Poddar carried out the threat and killed Tarasoff. Her parents filed a lawsuit, arguing that the therapist’s failure to warn Tarasoff contributed to her death. The court ruled that mental health professionals have a duty to warn individuals who are at risk of harm due to a patient's threats.

Legal Impact:
This landmark ruling established the duty to warn in cases where a patient poses a serious threat of harm to others. It significantly changed how therapists approach confidentiality, emphasizing that the safety of potential victims overrides the confidentiality agreement between the therapist and patient. This decision has been influential in guiding how therapists and mental health professionals assess and act on threats of violence from patients.

Case 3: State of Tennessee v. Mary C. Northern (1978) – Decisional Incapacity

Summary:
In 1978, Mary C. Northern, a woman with a severe mental condition, was hospitalized for a gangrenous leg infection. Despite the seriousness of her condition, Northern refused medical treatment, insisting that the issue was merely dirt on her leg. Medical professionals and her family were concerned about her decision-making abilities and sought legal intervention. The court found that Northern was unable to make informed decisions due to her mental illness and declared her decisional incapacitated. As a result, the court authorized medical treatment over her objection, acknowledging that her mental state prevented her from fully understanding the consequences of her decision.

Legal Impact:
This case set an important precedent in assessing decisional incapacity, particularly in medical situations. It emphasized that individuals who cannot understand the nature and consequences of their decisions, due to mental illness or cognitive impairment, may not be legally able to refuse treatment or make important decisions about their care. This case shaped the legal framework for determining when individuals may need assistance in making decisions, especially regarding medical and personal matters.

Decisional Capacity 

Decisional capacity refers to a person’s ability to understand, process, and make informed choices about their own life. It plays an important role in legal, medical, and ethical discussions, especially when individuals face cognitive impairments due to conditions such as dementia, intellectual disabilities, or mental illness.

For a person to have decisional capacity, they must be able to:

1. Understand information - grasp the nature and consequences of their decision.

2. Express a choice - clearly communicate their decision in a consistent manner.

3. Appreciate the impact - ecognize how the decision affects their personal situation.

4. Reason through options - Weigh the risks and benefits logically.

International Perspectives on Decisional Capacity

2006 UN Convention on the Rights of Persons with Disabilities (CRPD)
The 2006 UN Convention on the Rights of Persons with Disabilities (CRPD) promotes autonomy and equal rights for people with disabilities. It challenges outdated legal systems that place individuals under guardianship, where someone else makes decisions for them. Instead, the CRPD pushes for supported decision-making, allowing people with disabilities to make choices with guidance rather than having decisions made on their behalf.

Global Impact

• Encouraged legal reforms in multiple countries to recognize supported decision-making over traditional guardianship.

• Led to changes in healthcare and employment laws, ensuring individuals with disabilities can participate in decisions about their lives.

• Increased advocacy for disability rights, shifting from a protection-based model to an empowerment-based approach.

2010 Yokohama Declaration on Adult Guardianship
The 2010 Yokohama Declaration focuses on ensuring individuals, even those with cognitive impairments, retain some control over their decision-making. It emphasizes shared decision-making, where the individual participates in the process rather than having decisions imposed upon them.

Global Impact

• Influenced legal reforms in countries moving toward a less restrictive guardianship system.

• Encouraged family and community involvement in decision-making rather than full legal guardianship.

• Strengthened human rights protections for individuals at risk of losing legal independence

​​​​Insanity Defense

Legal defense for those who, due to mental illness, couldn’t understand the nature of their actions.

Established by M'Naghten’s Case (1843).

Requires proof that the individual could not distinguish right from wrong at the time of the crime.

Duty to Warn

Mental health professionals must warn potential victims if a patient makes a credible threat.

Established by Tarasoff v. Regents of the University of California (1976).

Balances patient confidentiality with public safety.

Decisional Incapacity

When a person is unable to make informed decisions due to mental or cognitive impairment.

Courts assess functional ability—whether they can understand, reason through, and appreciate their choices.

Established by State of Tennessee v. Mary C. Northern (1978)

Key Factors in Capacity Assessment

Understanding: Can the person grasp relevant facts?

Expressing a Choice: Can they communicate their decision clearly?

Reasoning: Can they weigh options and consequences logically?

Appreciation: Do they recognize the personal impact of their decision?

International Perspectives on Decisional Capacity

2006 UN Convention on the Rights of Persons with Disabilities (CRPD): Advocates for supported decision-making rather than full guardianship.

2010 Yokohama Declaration on Adult Guardianship: Promotes shared decision-making to protect autonomy while providing necessary support.