Atlanta (CNN) -- The day after little Jorelys Rivera's mangled body was found in a suburban Atlanta trash compactor, Ryan Brunn sat in a stark room for a police interview. He began with confidence, but ended with trouble.
Keith Sitton, a special agent with the Georgia Bureau of Investigation, hooked up the jeans-clad Brunn to a polygraph machine. Then, he fired off a series of questions to the 20-year-old maintenance man. A videotape of Brunn's polygraph test was released Thursday.
"Regarding that girl, do you intend to answer these questions truthfully?"
"Did you participate in any way in causing the death of that girl?"
"Did you cause the death of that girl?"
"Do you know for sure who caused the death of that girl?"
Sitton asked the questions three times. Each time, Brunn said he had nothing to do with Jorelys' killing.
By the end of the interview, Sitton knew better. Brunn had turned into a prime suspect.
In the videotape, he tells Brunn that he did poorly on the questions regarding his alleged participation in Jorelys' death and the disposal of her body.
"I can see you're not doing good on this test," Sitton says. "Those two questions are really bothering me."
"I'm not holding back," Brunn says. "I promise you. I'll take the test again."
But that was not an option for Brunn.
The next day, on December 7, he was arrested.
Eventually, he pleaded guilty and, standing before a judge in a Cherokee County courthouse, he described in detail how he enticed, molested and killed Jorelys, 7, in Canton, 40 miles north of Atlanta.
After he was sentenced to life in prison without the possibility of parole, Brunn hanged himself with his sweathshirt in a prison cell.
It was that polygraph test that was started Brunn's unraveling.
"I've been doing this for a long time," Sitton tells Brunn at the start of the session.
But Brunn seems not at all concerned about the questions he is about to face.
Some people think they can beat a polygraph test, said Dr. Peter Ash, a forensic psychiatrist at Emory University in Atlanta.
"The fact is that most of them can't do it," he said. "You can control how you look. You can't control how you sweat."
Besides, said Ash, criminals are not known for good judgment.
His shirt sleeve rolled up to his shoulders, Brunn begins by telling Sitton that on a scale of one to 10, he is a 7.5 on the truth meter. That he had lied the day before when police asked him whether he'd run the trash compactor at the River Ridge Apartments in Canton, where Jorelys's body was found.
"I should have just told the truth straight up," Brunn says. "But I didn't. I was scared."
Brunn tells Sitton that his family was originally from New York but he had been living in Dahlonega, Georgia. He moved to the Canton complex in November, where he was living at a discount and working in maintenance.
He'd finished 10th grade but no more. Sitton tells him it's never too late to graduate.
Brunn went to Honduras a few years back on a church mission to help rebuild houses for the needy.
Sutton asks him if he smoked marijuana. Brunn admits to smoking the night before.
He answers Sitton's questions with apparent ease, not as a man who had committed a heinous crime. Later in court, he would describe how he used a roller skate to lure Jorelys into a vacant apartment. He told the judge he made the girl undress and wanted to take her for "sexual purposes."
He said he got scared that she would go home and tell her parents what had happened. So he struck her with the skate, slit her throat and tossed her body into the compactor. He even taped a handwritten note telling investigators that Jorelys was in there, almost as though he wanted his crime to be discovered.
By the end of the polygraph test, Brunn's voice is slight. He appears more nervous and goes outside to smoke a cigarette.
When he returns, Sitton confronts him about his lies.
"There's something on this that you're not telling us. Something that you are keeping to yourself," he says. "What is it you're holding back? Because we're trying to solve this thing."
Brunn fiddles with his cell phone.
Sitton tells him not to worry about his calls, that he's got more important things to worry about.
"It's just written all over you. Something's bothering you."
"I am not bothered at all."
"You haven't told the complete truth about everything."
It turns out Brunn lied about smoking pot, as well. He had smoked that morning, not the night before, as he said previously. Sitton tells him that he is concerned about Brunn's marijuana habit.
Brunn says he gets high but "it doesn't make me crazy. I promise you that."
Before the video cuts off, Sitton asks Brunn about allegations he faced in Virginia before his move to Georgia. He had been accused of sexually fondling another girl.
"You know what I'm talking about," Sitton says.
"I don't," Brunn replies.
"Remember I said you had to be 100% truthful? I asked you if anyone made accusations. So what you done is told me a lie. You also lied about the trash compactor."
"They put things in that child's head," Brunn says. "I'm a good person. I didn't do nothing to that little Spanish girl and I didn't do nothing to (the other) girl."
There is little remorse in Brunn's words.
Later in court, he would tell Jorelys' family that he was sorry. "Lo siento," he said in Spanish.
But in front on Jorelys' sobbing mother, Brunn's apology fell far short.
Two days later, he, too, was dead.