Criminal Defense FAQ

How Does the Insanity Defense Work?

Proving that you are not guilty of a crime by reason of insanity is extremely difficult. Only about one percent of criminal defendants even raise the defense, and only a quarter of those are successful. While the legal definitions of insanity vary from state to state, the essential element of insanity defenses is that the defendants lacked the required “criminal intent” to make them legally responsible for their actions.

The most widely used legal definition of insanity is known as the M’Naghten rule, named after a famous English murder case from the 1800s. In a nutshell, the M’Naghten rule requires a defendant to prove either that he did not know what he was doing, or if he did, that he didn’t know what he was doing was wrong. Boiled down even further, a defendant is insane under M’Naghten if he didn’t know right from wrong. Another standard courts will use is called the irresistible impulse test. Under this standard, defendants must prove that they knew their acts were wrong, but couldn’t control themselves.

About one-third of the states use the American Law Institute’s test for insanity, which states that a people aren't responsible for criminal conduct if, as a result of mental disease or defect, they lack substantial capacity to appreciate the criminality of their conduct or to conform their conduct to the requirements of the law. This is a slightly more lenient standard than M’Naghten, as defendants must only show a “substantial incapacity” that they didn’t know that what they was doing was wrong, rather than having an absolute inability to know the difference.

There is good reason for having the insanity defense available, even if it is rarely used. Since putting people in prison for crime serves in part to deter future crime, it doesn’t make sense to put people in jail who had no control over what they were doing in the first place, or did not intend to do what they did. Most would also argue that treatment of the criminally insane in a mental institution is a more appropriate way to keep the public safe than prison. Rarely do those who are found not guilty by reason of insanity go free, and often their commitment to a treatment facility can last much longer than a prison sentence would have.

Copyright © 2008 FindLaw, a Thomson Reuters business

DISCLAIMER: This site and any information contained herein are intended for informational purposes only and should not be construed as legal advice. Seek competent counsel for advice on any legal matter.

Do the Police Need a Warrant to Arrest Me?

While it may seem surprising, in most cases the police do not need a warrant arrest you. It all comes down to probable cause — if the police have probable cause to believe that you have committed a crime, they can arrest you without going to a judge for a warrant first. In getting a warrant, law enforcement officers have to convince a judge that there is probable cause to make an arrest; if an arrest was made without a warrant, the police must later convince a judge that there was sufficient probable cause at the time the arrest was made.

So what constitutes probable cause? In general, probable cause exists when law enforcement have more than a “bare suspicion” that a crime has been committed, and that the person they want to arrest has committed the crime. The police don’t actually have to witness the crime; they just have to honestly believe it is more likely than not that the suspect was involved. Once of the most common bases for a warrantless arrest is where a witness to a crime gives a description of a perpetrator and the police see someone fitting that description nearby. In most cases, that is sufficient probable cause to justify an arrest for a felony offense. The same does not hold true for misdemeanors, however — an officer cannot make a warrantless arrest of someone for a minor crime (such as shoplifting) without having personally witnessed the crime.

Generally, police need an arrest warrant if they are planning to arrest a person in his or her home. This is not a blanket rule, however, and police can make a warrantless arrest in a suspect’s home if “exigent circumstances” exist. Exigent circumstances can include the following situations: when the police have chased a fleeing suspect into his home; when the police believe that someone might be in danger inside the house; or if a person (not necessarily the suspect) answers the door and lets the police come inside. In any of those cases, an officer may later justify the warrantless arrest even if made inside a suspect’s home.

If a judge later rules that there was insufficient probable cause for the police to arrest you, there remains little you can do. An experienced attorney may argue that any evidence gathered during the course of an unlawful arrest should be inadmissible during trial, but consequences of an unlawful arrest are evidentiary in nature.

Copyright © 2009 FindLaw, a Thomson Reuters business

DISCLAIMER: This site and any information contained herein are intended for informational purposes only and should not be construed as legal advice. Seek competent counsel for advice on any legal matter.

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