A recent quiz compiled by PBS gives drivers an easy way to "Spot the Illegal Police Stop." The 4th Amendment protects you against unreasonable searches and seizures, but it gives police a lot of leniency. So what exactly is legal and not legal?

Scenario 1: The Indiscriminate Checkpoint

In 1998 in Indianapolis, the police began setting up checkpoints around town to fight illegal drugs. One cop would conduct an open-view exam, while a second officer walked around the car with a narcotics dog. Is it a legal stop? Continue reading below

NO. The Supreme Court does allow the police to use roadblocks to check for illegal immigration or drunk drivers, but in the legal case Indianapolis v. Edmond, it ruled that a search conducted "in the absence of individualized suspicion of wrongdoing" went too far.

Case 2: A Robbery in Progress

An undercover cop sees two men in Cleveland, Ohio walking back and forth on a street and staring into the same store window more than 20 times. They huddle up after each time they look in the window. Then, a third guy joins them. The cop thinks they are casing the store and stops them, frisks them, and finds guns on two of them. Is it a legal stop?

YES. This legal case in 1963 established what's considered a legal "reasonable stop and search." In this legal case, Terry v. Ohio, the Supreme Court ruled that if an officer has reasonable suspicion that a crime may be in progress, he could conduct a limited search. This legal case is what allows "stop and frisk" today. Continue reading below

Case 3: Footprints in the Desert

The Border Patrol in Arizona sees human footprints in the desert as a group of people trespass the border from Mexico and walk to a pickup spot on the highway. After investigating, they pull over a driver who they suspect is the smuggler. The officers ID themselves and say that they are performing an immigration check. In the truck, they find another man whose shoes match the footprints found in the desert and six undocumented passengers. The suspected smugglers are arrested and charged with six counts of "transporting illegal aliens." Is it a legal stop?

YES. In this legal case from 1981, United States v. Cortez, the Supreme Court said that the police have the authority to stop someone if "the totality of circumstances - the whole picture" leads to a reasonable suspicion that criminal activity may be underway. In other words, they stopped them because they saw evidence and guessed that was the spot where the undocumented people were getting picked up during that time of day by a truck.

Case 4: The High-Crime Area

A man holding a bag is standing on the street in a Chicago neighborhood known for selling drugs. When he sees the police coming, he takes off running. The officers catch him, pat him down and find a handgun. The man is arrested and convicted of unlawful use of a weapon by a felon. Is it a legal stop?

YES. Older legal cases have established that being in a neighborhood known for selling drugs does not give the police a right to stop you. However, if the person runs away from the police, according to the Supreme Court, that gives them enough reasonable suspicion to go after them and stop them ∎

To read the whole article with all the legal details and take the quiz, please visit PBS.