Fate of killer who suffocated his wife, her young girls is in hands of the jury

Both sides in the case of Alberto Sierra, who admitted to snuffing the lives of his estranged wife and her two young daughters with a plastic bag, attempted to sway jurors for the final time Monday in the hopes that they vote to send him to Florida’s Death Row — or spare his life.

Prosecutors and defense attorneys sparred in closing arguments in Sierra’s death penalty sentencing trial. Sierra, 42, admitted to suffocating his estranged wife, Gladys Machado, 29, and her daughters Julia, 6, and Daniela, 3, with a plastic bag on Nov. 10, 2012. Their bodies were found three days later inside a closet at the Flagami home they once shared.

“They all had to die because that’s what that person, Alberto Sierra, decided was the best way to save himself,” prosecutor Abbe Rifkin said. “Three lives, three futures. One irreversible crime.”

“The question is not ‘Will Alberto Sierra die behind bars?’ because he will,” defense attorney Khurrum Wahid said. “The choice here is a moral choice.”

The fate of Sierra is in the hands of 12 jurors who are tasked with deciding whether Sierra, who pleaded guilty to the murders, should be condemned to death or sentenced to life in prison. Miami-Dade Circuit Judge Marisa Tinkler Mendez is presiding.

The jury is expected to begin deliberating on Tuesday morning, after Tinkler Mendez instructs them on the law.

READ MORE: Defense rests in death penalty trial of killer who suffocated wife, her girls

Rifkin told the jurors they are tasked with deciding what punishment “does justice for the brutal, selfish and deliberate killings” of Machado and her two young daughters. She urged the jury to examine the evidence, saying it should lead them to recommend a death sentence.

Rifkin recounted how an ordinary Saturday of shopping ended with Sierra leaving Machado, Julia and Daniela rotting in a closet and being eaten by insects. Sierra, Rifkin said, chose to suffocate a woman who loved him and her two girls, whose only crime was witnessing what had happened to their mother.

“Why are they all dead? Because Alberto Sierra wanted them dead,” Rifkin said. “Three people are in their graves for nearly 14 years because Alberto Sierra’s need for self-preservation, his selfish desire to take what he wanted without consequence.”

READ MORE: Evidence shows mother, 2 girls suffered ‘slow death’ as killer suffocated them

Looking on at the jury, Wahid highlighted that Sierra admitted to the “monstrous act” and will be held accountable.

“Anger, hate, utter disgust. You don’t feel that, you’re not human,” Wahid said. “You don’t feel that toward Alberto Sierra, that’s not normal.”

But Wahid urged jurors to put those feelings aside and consider the totality of Sierra’s life, most notably how he was pummeled by a car in 1996 while he was skating as a 12-year-old boy. Wahid held up a 3D-printed model of Sierra’s brain, which had a removable blue piece of plastic representing the area of the brain that neuropsychologist Erin Bigler testified Sierra is missing.

Bigler created the model and opined that Sierra had ”extensive brain damage” linked to a traumatic brain injury. He testified that a “hole in the frontal lobe” of Sierra’s brain was consistent with being hit by a car.

READ MORE: Killer who suffocated wife, her 2 girls has ‘extensive brain damage,’ expert says

“This is a real injury,” Wahid said. “This is an injury consistent with what …happen[ed] in 1996.”

Wahid said part of Sierra’s brain is “gone, nonexistent” — and his severe diabetes has likely also affected the way his brain functions. Sierra’s mother, Mercedes Pedraza, testified that Sierra wasn’t the same after the accident and had frequent tantrums, refused to follow rules and ultimately dropped out of high school.

Wahid also pointed to the nature of the grisly murders as evidence of Sierra’s “broken brain” — and asked jurors to vote to sentence Sierra to spend the rest of his life behind bars.

“This is not a normal, healthy brain,” Wahid said. “There’s a lot here that doesn’t make sense unless you look at it through that lens.”

Murders were ‘ice cold’

On the day of the murders, Sierra had joined the family on a shopping outing to Mall of the Americas to purchase a birthday gift for Daniela, who was days shy of turning 4. Machado had picked Sierra up from his mother’s Kendall home in her gold Nissan Altima.

At the mall, they bought clothes and took the girls out for ice cream. When they get back into Machado’s car, Machado received a call from a new love interest, enraging Sierra.

Sierra attacked Machado with a knife in the car, cutting her hand and causing her to bleed profusely. The girls, Sierra said, tried to defend their mother. He elbowed them to contain them in the backseat. Julia and Daniela, Sierra said, were repeatedly exclaiming “Papi, no, Papi, no.”

READ MORE: Killer calmly confessed to suffocating his wife, her 2 girls with a plastic bag

When they arrived at the home, Sierra said he wanted to check Machado’s phone, but Machado refused to give up her passcode. Sierra then tied Machado’s hands up with a nylon rope and threatened her with a knife. She ultimately gave him the passcode.

Machado was kidnapped, humiliated and tortured for hours, Rifkin said, with Sierra using her body as a “pin cushion for his knife.” Sierra stabbed, sliced and carved parts of Machado’s face and body before and after she died, the prosecutor said. The corners of her mouth were carved, and she had a curved slice on her chin under her lips that Rifkin said looked like a smiley face.

After several hours of tormenting Machado, Sierra placed his leg on her chest to keep her from moving and wrapped a yellow Sedano’s Supermarket plastic bag over her face. She was kicking and struggling, Sierra said, causing him to turn his face away so he wouldn’t have to look at her struggling to breathe.

Sierra ultimately decided to cut off Machado’s shirt and bra with a pair of scissors and had sex with Machado’s body. He told detectives he stopped 10 minutes into the act because it “wasn’t right.”

Sierra then he grabbed the same plastic bag he used to kill Machado, pulled back Julia’s hair and placed it over her face. Julia, he said in his confession to police, was kicking and trying to break free, so he used his body weight to restrain her and his knees to pin her arms to the bed.

Sierra told detectives he sexually assaulted the girl’s body for about five minutes before “realizing it was wrong.” But the blood and nature of the injuries to Julia’s genitals, which a forensic pathologist described as being “pulled apart,” indicated the child was alive and likely in significant pain during the rape, Rifkin said.

Sierra turned to Daniela, who was sleeping face down on her bed. Sierra said he crept up behind the toddler and straddled her body, covering her head with the bag.

“It doesn’t get colder than this,” Rifkin said. “This was ice, ice cold.”

Immediately after the murders, Sierra began trying to “save his own skin,” Rifkin said. He cleaned up the scene with bleach and dragged the bodies into the closet. At 8 p.m. that day, Sierra texted himself from Machado’s phone, writing “I’m not going to make it to ur house.” He deleted messages Machado had sent him when she was on her way to pick him up.

Rifkin also pointed out how Sierra feigned concern over Machado’s disappearance to family members and friends. Sierra even exchanged flirty texts with another woman days after the bodies were found.

“He acted completely normal because he had no guilt,” Rifkin said. “He did whatever he had to do.”

Sierra, Rifkin said, pleaded guilty in a last ditch effort to save himself. He made a ”conscious, cold, brutal” choice when he killed Machado, Julia and Daniela that had nothing to do with him being hit by a car as a 12-year-old boy.

“This is not a brain problem folks. This is a heart problem,” Rifkin said, adding that Sierra’s brain was “fully functional” when he deliberately terrorized the family for hours.

READ MORE: ‘You took them,’ man says to killer who suffocated his mother, sisters with bag

Julia and Daniela will never be able to grow up, graduate from high school and walk down the aisle at their weddings — and Machado will never get the chance to see her children reach those important milestones, Rifkin said.

“He has earned a life of greater restrictions that Death Row would bring.”

This story was originally published October 19, 2026 at 5:19 PM.