Houston Homicide Detective Sgt. Brian Harris knows how to fire a pistol and work a crime scene, like all cops do. But his real talent comes out in the interrogation room -- or as police like to call it -- "The Box."
"[The Box] is the place where it all happens," Harris says. "It can save a lot of families a lot of heartache. It makes sense out of all the nonsense and craziness of some of the deaths that we deal with."
Harris, who is considered the grand inquisitor of Houston Homicide Division, teaches his interrogation technique at the Houston Police Department academy and to other departments around the country.
ABC News' "Primetime: Crime" was granted unprecedented access to the inner-workings of the Houston Homicide Division, to explore how Harris plies his trade.
The police interrogation has been a staple of television cop shows for generations. From "Dragnet" to "Law & Order: SVU," there's something about the belligerent interrogations that keep you on the edge of your seat. But Harris says there's a big difference between Hollywood-style interrogations and the real thing.
"Yelling at 'em, smacking 'em, making 'em feel like a piece of dirt...at least here in Houston, Texas, it's not gonna work," he says.
Instead, Harris is known for a decidedly different technique.
"I treat them with dignity," he told ABC News' Chris Cuomo. "If they can see me as a person that views them with dignity, the chances of communicating are starting to open up."
Indeed, in the more than 12 unedited interrogations supplied to ABC News, most feature Harris as a cordial confidante.
In the case of one murder suspect, James McCann, who ultimately capitulated and was convicted of killing his estranged wife, Harris tells him, "Even when you wanted the divorce, you still took care of her. Not many men would do that, Jim."
McCann's case is one of three that will be featured on tonight's edition of "Primetime Crime."
While they lay out their alibis, Harris patiently observes the suspects, looking for telltale signs of deception. Some are subtle, such as when McCann tells Harris: "Honestly, I don't know what happened" when he's asked whether he murdered his wife.
Words like "'sincerely', 'honestly', 'truthfully'...L-Y is like a big red flag going up, because I'm like, 'Here it comes'...it's a qualifying statement," Harris says.
Then there are the non-verbal cues. Harris teaches his students to look for nervous grooming gestures like hair twirling, face rubbing, and above all, defensive body posture -- when a suspect closes himself off or backs away from his interrogator. Of course, one nervous indicator does not imply guilt.
"It's the totality of the whole package," says Harris. "You might lean back [during an interrogation] and be like...'Get out of my face, man. That's not what happened.' And you would create that distance."
Before an interview even begins, Harris makes sure the box is set up in a way that gives him a psychological edge. The walls are kept blank. The suspect's chair is on straight legs while the interrogator's is on rollers.
That way, "I may start off being three to four feet away...[but] when they're right about to confess...I may be within inches of them," he says.
And, just as he enters the room, Harris likes to run a little experiment.