Killer who suffocated wife, her young girls should be executed, Miami jury says

Miami-Dade County admin October 20, 2026 0 Comments

Killer who suffocated wife, her young girls should be executed, Miami jury says

Alberto Sierra, who admitted to snuffing the lives of his estranged wife and her two young daughters with a plastic Sedano’s Supermarket bag, should be executed for his crimes, a jury said Tuesday.

Sierra, 42, was stoic as the verdict was read before Miami-Dade Circuit Judge Marisa Tinkler Mendez. Sierra 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.

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

Loved ones of Machado, Julia and Daniela teared up and comforted each other on hearing the jury’s recommendation. The jury voted to sentence Sierra to death for the murders of Machado, Julia and Daniela after more than five hours of deliberation.

Jurors recommended death for Machado’s murder in an 11-1 vote, for Julia’s killing in a unanimous vote and for Daniela in an 8-4 vote.

After the jury’s verdict, Sierra will have another hearing and his formal sentencing. While a jury can recommend life or death, a judge has the final say on whether to impose a death sentence.

During closing arguments on Monday, prosecutor Abbe Rifkin urged the jury to recommend a death sentence because it “does justice for the brutal, selfish and deliberate killings” of Machado and her two young daughters.

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

Defense attorney Khurrum Wahid highlighted that Sierra admitted to the “monstrous act” and will be held accountable. Wahid also pointed to how Sierra was pummeled by a car in 1996 while he was skating as a 12-year-old boy. That incident, he said, left Sierra with a “broken brain.”

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

“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’

For a final time on Monday, Rifkin recounted how the ordinary Saturday of shopping ended with Machado, Julia and Daniela being brutalized and stuffed in a closet inside the home they once shared with Sierra.

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.”

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.

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

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.”

About an hour later, 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.

When confronted with the mounting evidence against him, Sierra confessed, detailing calmly how he snuffed the lives of Machado, Julia and Daniela with the yellow plastic bag, before having sex with the bodies of Machado and Julia.

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

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

This report will be updated as more information becomes available

This story was originally published October 20, 2026 at 6:28 PM.