Ignorantia juris non excusat.
It is a very old axiom of our legal system of justice that "ignorance of the laws is no excuse". Anyone who violates a law may not escape responsibility merely because they are unaware of its existence or misunderstands it. That means, for example, that if you or I possess an illegal drug, not knowing that it is an illegal substance, we can nevertheless be prosecuted for violating the law. It also means that if a police officer arrests a citizen without probable cause to believe a crime has been committed, the arrest is unlawful — even if the officer believed he had legal cause.
The reason for this legal doctrine should be obvious. If ignorance of the law were an excuse, then anyone arrested for a criminal offense could avoid prosecution by simply saying that they were unaware of that law. Similarly, an officer making an illegal arrest could simply claim that he mistakenly believed that it was legal.
Clearly, then, this ancient maxim of ignorance of law not excusing unlawful conduct applies to cops as well as citizens….or does it?
Court Rules for a Mistaken Officer
Washington, DC. Dec. 15 (New York TImes) – A police officer can stop a car based on a mistaken understanding of the law without violating the Fourth Amendment, the Supreme Court ruled on Monday in an 8-1 decision.
The case arose from a traffic stop in North Carolina based on a broken brake light. But state law there required only a single working “stop lamp,” which the car in question had.
In an opinion by Chief Justice John G. Roberts Jr., the Supreme Court ruled that the officer’s mistake was reasonable and so did not run afoul of the Fourth Amendment’s ban on unreasonable searches and seizures…
Justice Sonia Sotomayor dissented. She said the court’s ruling “means further eroding the Fourth Amendment’s protection of civil liberties in a context where that protection has already been worn down.”…
Chief Justice Roberts conceded that the court’s decision at first blush ran afoul of the maxim that “ignorance of the law is no excuse.”…
In recent years, we have seen increasing judicial decisions finding ways around the Constitution and our laws to justify unlawful conduct by law enforcement. One of the most glaring examples in the DUI field was the U.S. Supreme Court’s decision in Michigan v. Sitz — in which the Court somehow found an exception to the Fourth Amendment by allowing police to stop citizens at sobriety checkpoints with no reasonable suspicion that a crime may have been committed. In Chief Justice Rehnquist’s 5-4 decision, he admitted that these checkpoints were a violation of a citizen’s constitutional rights — but that they were only a "minimal intrusion", outweighed by the greater interest of the government in minimizing fatalities on the highways. See Growing Number of States Outlawing DUI Checkpoints.
Apparently, the Supreme Court has now clearly recognized that we have a separate set of laws that apply to police officers…and we now have a new legal maxim: "Ignorance of the law is not an excuse….unless you are a cop".