Miami-Dade jury weighs death penalty for Alberto Sierra in 2012 killings of his estranged wife and her two young daughters

A Miami-Dade County jury was set to begin deliberating Tuesday on whether Alberto Sierra should be sentenced to death for the November 2012 killings of his estranged wife, Gladys Machado, and her two young daughters, after prosecutors and defense attorneys delivered closing arguments Monday afternoon in a penalty-phase trial that has stretched for three weeks.

Sierra, 42, pleaded guilty in August, so the 12 jurors are not deciding whether he committed the crimes. Their only task is to recommend a sentence: death or life in prison without parole. Under a 2023 Florida law, a death recommendation requires the votes of at least eight of the 12 jurors. Miami-Dade Circuit Judge Marisa Tinkler Mendez will make the final decision. As of Tuesday, no recommendation had been reported.

What Sierra admitted

On Aug. 7, Sierra pleaded guilty to nine felonies: three counts of first-degree murder, three counts of kidnapping, two counts of abuse of a dead human body and one count of armed burglary, NBC 6 and WPLG Local 10 reported.

Machado, 29, and her daughters, ages 6 and 3, were suffocated with a plastic grocery bag on Nov. 10, 2012, the Miami Herald reported. Some earlier reports listed the younger girl's age differently. Their bodies were found three days later in a closet of a home in western Miami-Dade near Northwest Fourth Street and 73rd Avenue, in the Flagami area, where the family had once lived. Miami-Dade Fire Rescue crews who responded after a neighbor noticed a foul odor testified about the discovery on the second day of the trial, CBS News Miami reported.

According to the arrest affidavit described by NBC 6, the couple, who were married but living apart and had no children together, argued during an outing at the Mall of the Americas, and Sierra pulled out a knife and drove Machado and the girls to the home. Prosecutors said he accused Machado of cheating, held her captive and tortured her for hours, and later killed all three. Prosecutors also said he sexually assaulted two of the victims. Investigators had questioned and released Sierra before he gave a full confession, which jurors heard on a recording in which he said he went crazy, according to reports.

Machado's son, Michael Padrino, survived because he stayed home that day with his great-grandmother. Now 19, he testified on Oct. 6 and confronted Sierra from the witness stand. "We were supposed to have more time together," he told the court, NBC 6 reported.

The case for death

Prosecutor Abbe Rifkin urged jurors to recommend death, describing the killings as deliberate, calculated and especially cruel. She told jurors that Sierra cleaned the scene with bleach, moved the bodies into a closet and sent texts from Machado's phone to make it seem she was alive, according to the Herald, and that he feigned concern about her disappearance and exchanged flirtatious texts with another woman days after the bodies were found. "It doesn't get colder than this," Rifkin said.

"This is not a brain problem folks. This is a heart problem," Rifkin said, according to the Herald. She also told jurors that Sierra "chose death, at every opportunity," CBS News Miami reported. Earlier in the trial, prosecutor Lara Penn argued that Sierra's efforts to cover his tracks and mislead investigators and family showed planning and an understanding of what he had done.

The case for life

Defense attorney Khurrum Wahid asked jurors to spare Sierra's life, arguing that a childhood brain injury changed him. Sierra was hit by a car in 1996, at age 12, a few months after he moved to the United States from Cuba, the defense said. Neuropsychologist Erin Bigler testified that Sierra has extensive brain damage consistent with that injury, and the defense also argued that severe diabetes may have affected his brain function. Sierra's mother, Mercedes Pedraza, testified that he changed after the accident, throwing frequent tantrums, refusing to follow rules and eventually dropping out of high school, the Herald reported. The defense also pointed to a diagnosed personality disorder. "No one chooses to have a mental disorder, just like no one chooses to have brain damage," Wahid said, according to CBS News Miami.

The state countered with its own expert, a neuropsychologist who testified that Sierra's memory test results suggested he was exaggerating his memory problems, WPLG reported. Under cross-examination, Bigler agreed that planning after a crime requires executive function, NBC 6 reported. Sierra declined to testify.

"The question is not 'Will Alberto Sierra die behind bars?' because he will," Wahid told jurors, according to the Herald. "The choice here is a moral choice."

A three-week penalty phase

The trial has moved through the following stages, according to reporting by NBC 6, CBS News Miami, WPLG and the Miami Herald.

On Oct. 14, Tinkler Mendez dismissed a juror who wrote to her that the case was causing him emotional distress and sleeplessness, NBC 6 reported. The juror also raised questions about the trial's cost to taxpayers and whether a fundraising page for the victims would be appropriate. The judge said she had never experienced such a situation in her career.

How Florida's death penalty law applies

Florida lowered its threshold for death recommendations in 2023, when the Legislature replaced a requirement for a unanimous jury with the current rule that at least eight of 12 jurors must agree. If fewer than eight jurors vote for death, the judge must impose life in prison without parole. If eight or more recommend death, the judge may impose either sentence.

What's next

Deliberations were expected to begin Tuesday morning after Tinkler Mendez instructed jurors on the law, the Herald reported. Once the jury returns its recommendation, the judge will schedule further proceedings before imposing a sentence. Whatever the jury decides, Sierra will spend the rest of his life in prison: the only question before the panel is whether he should also face execution.