Professional
Formal
IVT
nexus requirement
Pronunciation: NEK-səs
Legal mandate that mental illness must be causally connected to the criminal behavior for insanity defense.
Full Definition
A legal principle requiring that a defendant's mental illness must have a direct causal relationship to the criminal conduct for a successful insanity defense. The mere presence of mental illness at the time of the offense is insufficient; the illness must have substantially impaired the defendant's cognitive or volitional abilities in ways that directly relate to the criminal behavior. This requirement prevents defendants from claiming insanity based solely on having a mental health diagnosis.
Usage
Usage note: Critical concept in insanity defense evaluations and testimony.
In Context
- "The prosecution challenged the nexus requirement, arguing the defendant's depression was unrelated to the theft." — Trial transcript
- "Expert testimony must establish a clear nexus between psychosis and the defendant's actions." — Expert report
Also known as
causal connection
but-for causation
Don't confuse with
proximate cause
product test