He became even more intent about learning the language after working as an officer on the streets of Phoenix -- "You have to be able to communicate with people," he says. It also helped when he married a woman whose family is Mexican.
Phoenix PD certified him as a translator in 2000, and he joined the agency's Foreign Prosecution team -- where fluency in Spanish is a must -- in 2004.
Case detectives Ballentine and Schechterle will monitor the interview on a television screen across the hall.
"Hey, John," Ballentine tells Shallue. "If you get stumped on any Spanish words in there, just ask me."
"Sí, señor," Shallue replies.
The detective first gives the suspect a bottle of water, and tries to verify his name and address. Abelardo continues to say he's Garcia-Ruiz, a native of Mexico City.
"Look at me," Shallue tells him in Spanish. "I know who you are, and I don't want you to lie to me. I have photos of you, and I've spoken to your family. So tell me the truth."
Shallue hands the man a form to sign that will cause police to notify the Mexican consulate of his current detention.
He signs the form "Abelardo Jarquin-Lopez."
That's a huge admission in this dance between the detective and his prey.
Abelardo now tells Shallue he's been in the States on and off for about seven years. He admits he's a coyote and is paid $400 for every person he smuggles into the States.
Fourteen minutes into the interview, the detective raises Margarita's name for the first time. Abelardo shakes his head from side to side, as if to say he's never heard of her, but Shallue is insistent.
Abelardo soon admits he was at the La Quinta in April 2005 with his sister-in-law, Margarita Parada-Alavez. He says he was charging Margarita's "husband" $1,000 to get her to Atlanta.
Abelardo says he, his brother Alfonso and two other coyotes were waiting for someone to bring about 20 more illegal aliens to the motel, which is why they'd rented three rooms.
Abelardo claims he'd been in Room 121 with Margarita and two of his coyote colleagues when "la mataran" -- they killed her.
He says he doesn't know who "they" were.
Abelardo says an unknown man had come into the room brandishing a revolver, and had bashed him in the nose with it. Then, the attacker had forced him and another coyote named Alfredo into a car.
At a house somewhere in Phoenix, the kidnappers (there were others waiting there) had demanded $10,000 from Abelardo's brothers.
But Abelardo and his pal were able to escape from their captors after a day, and immediately split for Nogales. From there, they'd gone to Mexico City.
Shallue replies by telling Abelardo about the uniqueness of his fingerprints and DNA, and that the evidence will reveal if he's lying.
"Do you know that Margarita called her brother Balfre from the motel?" the detective asks Abelardo.
"No," the suspect replies after a longish pause, thrown by the out-of-left-field question.
Shallue says he knows Margarita had expressed great fear in her last call to her brother Balfre because Abelardo was trying to rape her.
"Be a man," the detective says. "Stand up. If you lie to me, and I can show you're lying to me, you'll be in a lot of trouble. If you tell the truth, it will help you. I don't think this was planned. I think it was a mistake. I don't think it was premeditated. Just one of those moments. How did this happen?"
Abelardo says he doesn't know what happened, and that he'd been intoxicated on booze and cocaine.
Shallue now asks him straight up why he "did it."
"I don't know," Abelardo replies.
It's not a full confession, but close.
"When did you realize what you had done?" the detective asks.
"When she was dead."
Abelardo says he can't explain why Margarita was naked from the waist down, or how she'd ended up in the bathtub.
Then, as if the magnitude of his near-confession has hit him, Abelardo quickly retreats.
Now he says another coyote named Alejandro had been in Room 121 all evening with him and Margarita. Abelardo insists that he'd found Margarita dead in the bathroom, and that's all he really knows.
"But in a sense, Margarita told us what happened when she was talking to her brother on the phone in the bathroom," Shallue explains, before excusing himself from the room.
The detective confers briefly with Jack Ballentine, telling him that federal authorities could charge Abelardo with murder because Margarita died while being smuggled into the States.