He killed his wife and her two young girls. Jury will decide if he gets to live

In a Miami courtroom on Friday morning, a man admitted to suffocating his estranged wife and her two young daughters with a plastic bag nearly 14 years ago.

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In an orange jail jumpsuit, Alberto Sierra, 42, stood up, towering over his defense attorney Joyce Brenner, and pleaded guilty before Miami-Dade Circuit Court Judge Marisa Tinkler Mendez. His change of plea was not a result of a deal with prosecutors.

“Yes, ma’am,” Sierra said after the judge emphasized that he is facing the death penalty. “It’s been 14 years, so …”

Sierra was charged with three counts of first-degree murder and kidnapping, two counts of abuse of a human body and one count of burglary. His sentencing trial is set to begin with jury selection on Aug. 17. The 12 jurors who will be chosen for that case will be tasked with deciding whether Sierra should be condemned to Florida’s Death Row or sentenced to life in prison.

Gladys Machado, 29, and her daughters Julia Padron, 8, and Daniela Padron, 4, were killed on Nov. 10, 2012. Three days later, a neighbor found their bodies inside a bedroom closet in their Flagami home on the 7300 block of Northwest Fourth Street.

When questioned by police days after the murders, Sierra confessed to the grisly crimes:

He told detectives that he stabbed Machado inside her car after she, in his presence, took a phone call from another man. He then drove her and her daughters to their home. There, Sierra suffocated them with a plastic bag.

Sierra also raped Machado and Julia after they were dead, investigators say. DNA samples taken from Julia matched Sierra. Fingerprints at the scene were also linked back to Sierra, according to prosecutors.

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Machado and Sierra, who had a history of domestic violence, split up shortly before the killings. Machado, a mother of three, moved in with her grandmother in Homestead while Sierra stayed with his mother at her townhome in Kendall.

On the evening of the murders, Machado went on a shopping trip with her two daughters, leaving her 6-year-old son with her grandmother, court records indicate.

Sierra accompanied Machado and her daughters to the Mall of the Americas in Machado’s 2004 gold Nissan Altima. A woman living at an efficiency near the home saw the Altima that night but said it was gone by 11:30 p.m.

The Altima was not spotted again until Nov. 19, when officers discovered it parked in a guest spot at Kendall’s Calusa Club apartments, 8810 SW 132nd Ave., across the street from the home of Sierra’s mother.

The Altima was backed into some bushes “so as to conceal the tag number,” according to police. Inside, investigators found blood on both the passenger and driver’s side seats.

The murders unfolded five months after Sierra was released from jail for violating probation after police located a gun inside the home. Sierra, who had been convicted of drugs and weapons charges, could not possess a firearm.

The Department of Children and Families investigated Sierra because Julia told a teacher her stepfather had “bit me with his teeth.” Child-welfare investigators determined that the bite was child abuse, although Miami-Dade police concluded that Sierra had bitten the girl “playfully.” No charges were filed.

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This report was supplemented with information from the Miami Herald’s archives

This story was originally published August 7, 2026 at 12:07 PM.