Thieves are robbing someone, somewhere in this country every 15 seconds. And 75% of those robberies are homes. Tonight, abc's deborah roberts with a master thief, revealing what makes one home easier... See More
Thieves are robbing someone, somewhere in this country every 15 seconds. And 75% of those robberies are homes. Tonight, abc's deborah roberts with a master thief, revealing what makes one home easier to rob than the next. Reporter: Believe it or not, a home robber is as choosey as a home buyer. Anything here look enticing? Chris patterson ought to know. He's a former thief. And he says some houses just scream "rob me." And others, not so much. His big tip? A security system is worth it. Especially if it has cameras. In fact, some can even beam live video of a break-in as it's happening. Two people in the house. Oh, here comes another one. Reporter: So, a homeowner can call the cops. Man, it's okay. Officers are surrounding your house. Reporter: But get this. Patterson says he's still robbed plenty of homes protected by alarms. How? Because their owners are often too lazy to turn them on. Half the time, it's not even armed. Reporter: Not even armed? Really? On the flip side, here's a little something that's always on -- beware of dog signs? Not even going near it. Reporter: Patterson confesses all you need is a beware of dog sign. You can skip the actual dog. Automatic no-no. Reporter: So, if that's what turns him away, what attracts him to your home? Now, see this one is completely obstructed. Reporter: Is that a good thing or a bad thing? That's a great thing for a burglar. Reporter: That's because privacy makes his job so much easier. The same privacy you think, I love the privacy of having my backyard and not having people look in. I walk through the gate to your backyard and ingo, I love the fact that you have these beautiful shrubs up, now I can do my job without anybody see me. How many homes has he robbed? Reporter: He guesses maybe 100 over the years. He knows what he's talking about. He said he's more deterred by a dog sign than a security system? Well, because what he found over the years is that many people don't put them on, david, when they leave the house. And he can look sometimes in the window and tell and he's willing to take that chance. Looks to see whether that light is blinking. I know you have two important tips later tonight on jewelry and electronics. That's tonight on "20/20," true confusions from a thief, a pilot, a window washer what they all know, what they've all seen tonight about 10:00, 9:00 central.
This transcript has been automatically generated and may not be 100% accurate.