"If they have food in front of them and they don't eat or they're having a hard time eating, that tells me I might have a shot at this person," he says. " They have a conscience. They have a soul."
After all, how many of us, when we're so upset, have tried to eat a meal?
In a second case profiled by "Primetime Crime," police were called to a local Houston park in the wee morning hours of August 9, 2006. Gunshots were reported and police discovered the bullet-riddled body of 15-year-old Jose Lorenzo.
"He was a beautiful and handsome boy. He was, and he is, my angel," Jose's mother, Judith Anderson, told ABC News.
Jose's cell phone records indicate that minutes before his murder, he received numerous calls from a friend, another 15-year-old named Frank Spencer. Spencer's mom said her son, a minor, could be brought in for questioning. But since Spencer was not under arrest, Harris was not required to read him his Miranda rights. In other cases where mirandizing the suspects is required, Harris often gets them to talk anyway, telling them that waiving their rights is the only way he can hear their side of the story. Is it manipulative? Maybe. Is it legal? Absolutely.
In Spencer's case, it doesn't take long for Harris to develop a theory: "[Frank] is part of a gang and the gang asked Frank [Spencer] to help kill his friend."
But getting Spencer to confess would be another matter. First, Harris leverages his personal connection to Spencer. Harris and Spencer's mother attend the same church. He uses that fact to soften up the suspect.
"Your mom, number one, loves you," Harris tells him. "And number two, works her ass off for you, OK? You at least need to be able to explain how you got wrapped up in all this."
Spencer later told ABC News: "That was a shocker at that point...I'd go, 'Well, how did this man know so much about me?'"
Harris also gives Spencer the impression that his fellow gang members are at the station ratting him out. Cops call this bluffing. Defense attorneys call it lying.
"Unfortunately for the defendants and the suspects in America, the courts have blessed officers being able to lie to suspects about evidence," says Houston defense attorney Danny Easterling.
At the time of the interrogation, none of Spencer's friends had yet spoken to the cops, but the bluff is enough to seemingly make Spencer nervous -- so nervous that he begins to exhibit what Harris calls the "surrender position." With Spencer's head down and his foot tapping, Harris knows he's onto something.
"We're being told that you're the shooter," Harris tells Spencer. Spencer, defeated, says, "Yeah, I shot him."
ABC News also saw Harris use the bluff in another case, this one involving Christine Paolilla who was accused of shooting and killing four people -- two of whom were her close high school friends.
Paolilla is emphatic on the interrogation tape. "I had nothing to do with this," she tells Harris.
"I was also running a bluff on her," Harris admits. "Letting her think that we had her boyfriend, Christopher Snider, in custody, which we didn't."
Before that, however, Harris tried to get a sense of Paolilla's guilty conscience by asking her a simple question: "Do you believe you deserve justice or mercy?"