It is axiomatic that ignorance of the law is not an excuse. The US Supreme Court ruled Monday there is an exception to this rule: police officers. Stated in context, the exception applies to police officers in the case of a traffic stop based on the officer’s erroneous understanding of the law.
In Heien v. North Carolina, a police officer conducted a traffic stop on the basis that the subject car’s taillight was inoperable. However, the officer was wrong in his belief that the faulty taillight violated North Carolina’s Rules of the Road. During the traffic stop, the officer found cocaine in the car, leading to the arrest and conviction of the driver. The driver appealed the conviction on the “fruit of the poisonous tree” doctrine, which stands for the proposition that any evidence (“fruit”) seized during an illegal search (“poisonous tree”) cannot be used at trial. The driver argued that given the traffic stop was not based on illegal activity, the officer’s later seizure of the cocaine was illegal.
The Supreme Court disagreed with this application of the doctrine, ruling that the Fourth Amendment deals with “unreasonable seizures” and that officers need to act “reasonably” not “perfectly.” In effect, a reasonable misunderstanding of the law by the police can indeed satisfy the Constitution in this context.
