Following the plea, the defendant and Case Manager complete the intake, which gathers information about the defendant’s medical issues, substance use, mental health, family, education, employment, and convictions (doj.gov)
Having these principles makes it easier to go off what the person grew up like and what could have caused him to be mentally ill or become mentally ill giving a reasonable cause to believe insane or not helping jurors make a more accurate depiction of what happened nor only with opinion.