Criminal Defenses

When individuals are arrested for a crime their thoughts often turn to defending themselves against the accusation.  Ask police officers, for example, what they hear from alleged offenders during the arrest.  They may here, “But I didn’t do anything,” or “I was defending myself.”  During a routine traffic stop, the officer may hear “Officer, I honestly did not know that the speed limit dropped from 65 to 55!”  Thus, offenders may argue that they are absolutely innocent, that they were defending themselves against another person’s actions, or they may claim ignorance.  In some cases, offenders may use intoxication as a defense; in domestic violence cases this often occurs.  The offender will express remorse (at least at times) and beg to be forgiven, blaming his (or her) actions on the fact that he was intoxicated at the time and point to the fact that he does not engage in abusive behavior against his significant other when he has not been drinking. 

Sometimes offenders and their attorneys will claim that their actions were justified based on the consent of the victim (e.g. in a rape case) or that they were being blackmailed and their family members threatened by someone else who was leaning on them to commit a crime (e.g. taking funds from one’s employer, such as bank employee). 

The well-known insanity defense is based on the notion that a person was not capable of forming mens rea (intent to commit the offense; or, guilty mind).  There are many types of defenses under the more general umbrella of “insanity”, including:

1.  The irresistible impulse test (1834) says that a person may have known that the act that he/she was about to commit was wrong, but was unable to control the behavior nonetheless; and,
2. The substantial capacity test (American Law Institute) – “the lack of substantial capacity to control one’s behavior….not having the mental capacity needed to understand the wrongfulness of an act…”

We can trace the insanity defense back to England and the 1843 M’Naghten rule that defined a person as insane if at the time the act was committed, the person was laboring under a defect of reason that resulted from having a diseased mind.  This rule has come to be thought of as the basic question of, “Did the person know that what he/she was doing was wrong?”

How often is the insanity defense in the U.S. successful in getting offenders acquitted?  According to the Washington Post (see the link below), only in 1% of cases (based on a study that included evidence from eight states in the U.S.) is the insanity defense used. In those cases, only about 25% are successful.