On a long drive from Virginia, I thought I was traveling at a reasonable speed, but the flashing blue lights in my rearview mirror made me realize that I'd been over the limit. I handed the officer my license and made small talk while my wife dug through the glove compartment for the registration.

"I'm usually very careful about my speed," I told him as my wife handed me the paperwork.

The officer studied it and then gave it back. "Sir," he said gruffly, "this is not your registration."

Apparently I had handed him a warning ticket that I had received for speeding in South Carolina.