"Wherever you go you leave behind a trace of yourself; but you also take with you a trace of the place you’ve just been." That’s true! It’s what CSI cops know for sure. Of course, canvassing the crime scene, interviewing suspects, and following up leads are still the lifeblood of police work.

Then there’s "clown forensics," involving creative investigative techniques that work only if the detectives can keep a straight face.

For example, two detectives interrogate a suspect by putting a spaghetti strainer on his head as a "lie detector." He believes it works — so it does.

Another creative tactical deception I once heard about is "neuron skin particle testing," used occasionally in some small towns between Charleston and Spartanburg. The chief says he "needs leverage" to get suspects to confess, so he invents this lab test: Early in the interview, the chief tells the suspect, "Humans lose about 10,000 particles of skin every day. That’s where house dust comes from." That is scientific fact!

The chief shows the guy blowups of partial fingerprints, blood matching, DNA testing, and, of course, "neuron skin particle testing." The latter makes real good fiction. Most criminals get their legal education from television. This suspect probably sees television shows about police science and he believes nearly anything is possible in the laboratory.

Says the chief, "Preliminary lab results indicate that you were in the room where the body was found." In truth: There are no lab results, but the criminal suspect doesn’t know that. Tiny beads of sweat appear on the suspect’s forehead. He’s thinking they’ve found his "skin particles." He challenges the chief, asking how the test works.

"I’m sorry," says the chief, "it’d be a departmental violation to reveal that process outside of the courtroom."

Most suspects roll over in a couple hours. But you might wonder, "what about innocent people?"

The chief explains with a smile: "The test has no effect on innocent people. If they weren’t at the crime scene, their skin particles will not be present." Sounds reasonable to me.

NOTE: While Bob Ford is "on vacation" recovering from recent surgery, we offer one of his most popular columns from the past.