Alexandria, Va., Police Department spokeswoman Amy Bertsch has been researching this question. Here is some of what she learned.

You probably have seen a police officer giving someone a speeding ticket. Odds are the officer used a high-tech radar gun to figure out how fast the driver was going.

In the early 1900s, Alexandria's policemen (they were all men in those days) didn't have fancy technology, and people didn't have cars. They rode trains, horses and bicycles. But mostly, they walked.

So when cars first appeared on the city's roads in 1910, officers had to adjust, even though they were still patrolling on foot.

Police relied on pocket watches and some creative thinking. By stationing officers on the corner of several city blocks, they timed how long it took a vehicle to travel around them. Then, if a car or motorcycle went too fast - travelling two blocks in less than 25 seconds - they would know it.

Once police figured out who was breaking the law, they used hand signals or waved at officers down the road in an attempt to stop the speeding motorist.

Usually it worked. "But it sure wasn't easy," Bertsch said.

In many cases, the motorist was asked to drive to the local police station to be issued a $10 ticket. It was a real test of the honour system.

Alexandria's police force didn't get cars until 1920.

It wasn't any easier for Alexandria police to catch really bad guys a century ago. Back then, officers relied on a person's facial measurements to make an identification.

Later, when police began using fingerprints, the only tool experts had was their eyes: They looked at a suspect's fingerprints and compared them with fingerprint records kept on cards. The cards were stored in many locations, however, so they had to be collected before the identification process could begin. Matching two sets of prints often took months.

Today, thanks to computers, a match can be made in less than two hours, according to the Federal Bureau of Investigation (FBI). The FBI has kept the nation's fingerprint records since 1924. Currently, the prints of more than 47 million people are stored in its electronic Criminal Master File.

Finding wanted suspects also was more difficult 100 years ago. Posting a notice on the Internet or sending an e-mail wasn't possible, of course. Instead, police departments mailed each other letters (the kind that need postage stamps) or sent telegrams.

For example, if officers in Alexandria were looking for a suspect in a bank robbery, they might write to police departments across Virginia. The letters would include a description of the suspect and a question: Is there anyone fitting this description in your jail?

The system worked, although it could take weeks to get an answer.

—Leef Smith / LATWP