A defendant may raise as an affirmative defense that, at the time of the conduct charged, as a result of mental illness the defendant lacked substantial capacity to appreciate the wrongfulness of his or her conduct. If this is established, the trier of fact must return a verdict of “not guilty by reason of insanity.”103
A defendant may also raise as an affirmative defense that, at the time of the conduct charged, the defendant suffered from a psychiatric disorder that substantially disturbed the defendant’s thinking, feeling or behavior and/or that such psychiatric disorder left the defendant with insufficient willpower to choose whether or not to do the act, though he or she was physically capable. If proven, the trier of fact must return a verdict of “guilty, but mentally ill.”104
A defendant intending to rely on a defense of insanity, i.e., diminished capacity, must notify the Attorney General in writing, within the time provided for the filing of pre-trial motions or such later time as the court may direct, of such intent, with a copy of such notice filed with the Prothonotary.105 Failure to do so will preclude asserting an insanity defense, although the court may for cause shown allow a late filing.106 A subsequent withdrawal of an intention to assert a defense of insanity or mental illness is not admissible in any civil or criminal proceeding against the person who tendered such notice.107
If the defendant intends to introduce expert testimony on the issue of insanity or mental illness, the defendant must notify the Attorney General within the same time frame required for tendering notice of a mental illness defense.108
In an appropriate case, the court may, upon motion of the Attorney General, order the defendant to submit to an examination. No statement made in the course of such examination by the defendant or any testimony of the psychiatrist based upon such statement or any fruits of the statement are admissible against the defendant in any criminal proceeding except on an issue respecting mental or emotional condition on which the defendant has introduced testimony.109 Failure to comply with an order requiring examination may preclude the assertion of a defense of mental illness.110
At trial, a psychiatrist will be allowed to testify as to the nature of the examination of the defendant and the diagnosis or the mental condition of the defendant at the time of the commission of the crime. The psychiatrist may also give an opinion as to the capacity of the defendant to appreciate the wrongfulness of his or her conduct or to choose whether or not to do the act or whether, as a result of mental illness or defect at that time, the defendant was capable of having a particular state of mind which is an element of the offense charged. The psychiatrist can make any explanation reasonably necessary to clarify the diagnosis and opinion and may be cross-examined as to any matter bearing on the psychiatrist’s competence or credibility or the validity of the diagnosis or opinion.111
It is not a defense if the alleged mental illness or psychiatric disorder was proximately caused by the voluntary ingestion, inhalation or injection of intoxicating liquor, any drug or other mentally debilitating substance or any combination thereof, unless such substance was prescribed for the defendant by a licensed health care practitioner and was used in accordance with the directions of such prescription.112
103. 11 Del. C. § 401(a).
104. 11 Del. C. § 401(b).
105. Super. Ct. Cr. R. 12.2(a),(b). See also Comm. Pls. Ct. Cr. R. 12.1; Fam. Ct. Cr. R. 12.1.
106. Super. Ct. Cr. R. 12.2(a), (d). See also Comm. Pls. Ct. Cr. R. 12.1; Fam. Ct. Cr. R. 12.1.
107. Super. Ct. Cr. R. 12.2(e).
108. Super. Ct. Cr. R. 12.2(b).
109. Super. Ct. Cr. R. 12.2(c).
110. Super. Ct. Cr. R. 12.2(d).
111. 11 Del. C. § 402.
112. 11 Del. C. § 401(c).
© 2010 David L. Finger