Unless you’ve dedicated a lot of time to breaking the law, most of what you know about the cops comes from movies and TV, and those may or may not be just the facts, ma’am. All month, Ken Jennings will be exploring the “thin blue line” between police fact and police fiction. If you actually thought this stuff was true—well, you have the right to remain silent. Anything you say can and will be used against you in the comments section.

Police Myth #2: Police Mark Murder Sites with Chalk Outlines.

If you’re ever murdered, don’t worry about trying to strike some hilarious pose. The old cliché of the tape or chalk silhouette might be a nice visual crutch for a cop movie or TV show, but the police aren’t supposed to outline murder victims anymore, if they ever were.

Why not? Because it would contaminate the crime scene. Instead, photographs are taken of the body and its surroundings, along with a series of measurements to fixed reference points. (You know, like in the immortal Bunk-and-McNulty “Fuuuuu…” scene from the fourth episode of The Wire.) Occasionally dots, lines, or boxes of fluorescent paint might be used to make photos clearer, especially when the victim is a traffic fatality, on dark pavement, at night. But these aren’t really outlines, and crime labs get very annoyed if any of the paint touches any actual evidence.

A 1996 book about homicide investigation notes that the outlined bodies on TV have taken their toll on modern crimefighting. Some uniformed cops have been brainwashed by years of Law & Order reruns into thinking that they’re actually supposed to outline bodies, which has led to the rise of so-called “chalk fairy” contamination. “‘Chalk fairy,’” the author explains, “is a term used to describe mysterious police officers who feel the need to draw lines around the body and then disappear when investigators attempt to find out who contaminated the scene.” Since the “chalk fairies” of tomorrow are now watching CSI instead of Dragnet, I hope they’re learning a whole new array of unrealistic forensic techniques.

Quick Quiz: Chalk deposits make up the famous “white cliffs” of what British port town?

Ken Jennings is the author of Because I Said So!, Brainiac, Ken Jennings's Trivia Almanac, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.