The jury deliberating whether Alberto Sierra should spend his life in prison or face the death penalty recently heard a chilling VHS recording. In it, the accused, with a calm and almost indifferent tone, detailed how he murdered his estranged wife and her two young daughters in November 2012. This crime is considered one of the most horrifying in Miami-Dade in recent decades.
This session was part of the sentencing phase, during which Sierra sat emotionless as the 12 jurors listened to his confession, recorded on November 19, 2012—days after the murders and the discovery of the bodies.
The recording revealed, in Sierra's own words, how a jealousy-fueled argument spiraled into the tragic deaths of Gladys Machado and her children, Julia and Daniela Padrino, who were suffocated with plastic bags.
Jealousy Leads to Triple Murder
According to the confession presented to the jury, Sierra and Machado, who were separated, took the girls to the Mall of the Americas for ice cream. In the parking lot, Machado received multiple calls from a man, which she ignored. Suspecting infidelity, Sierra became jealous and attempted to uncover the caller's identity.
"I was furious," Sierra admitted during the interrogation. He wanted Machado's phone password to find proof of her alleged affair. The argument escalated, leading to a struggle over a knife, as outlined during the trial.
Prosecutors argue that after seizing the weapon, Sierra forced Machado and the girls to return to the home they once shared, located on Northwest Fourth Street in Flagami. There, he locked the girls in a room and continued to demand Machado's phone code.
Tragic Events Unfold
Machado's refusal led to a violent escalation. Sierra tied her wrists with a white nylon cord and injured her with the knife while insisting on the phone code, as presented during the hearing.
In the recording, Detective Juan Carlos Chaidez of the Miami-Dade Sheriff's Office asked Sierra if he knew he was in custody for the murders of Gladys, Julia, and Daniela. "Yes," Sierra replied. "I tied her hands behind her back."
Using a yellow plastic bag from Sedano's supermarket, Sierra narrated how he suffocated Machado, who resisted as he held the bag over her face.
Sierra later claimed he cried over his actions. However, the violence did not end with Machado. He recounted to detectives his subsequent murders of Julia, six, and Daniela, three, who both met the same fate.
Chilling Confession and Evidence Tampering
The confession also touched on Sierra's actions after the murders. The prosecution alleges Sierra sexually assaulted Machado and Julia's corpses and disfigured Machado's face with a knife, claiming he wanted to ensure she would never be beautiful for another man.
Sierra detailed his efforts to clear evidence from the house, listing areas he cleaned in response to Chaidez's questions. The bodies remained hidden in the master bedroom closet until a neighbor, alerted by the strong odor of decomposition, discovered them on November 13, 2012.
DNA Evidence and the Defense Strategy
Initially, Sierra lied to investigators about the events. However, when confronted with DNA evidence, his demeanor changed. Detective Chaidez noted Sierra's physical reaction, which led to his confession.
The defense, led by attorney Joyce Brenner, questioned the interrogation's tone and argued that Sierra's calmness was unusual. They aim to convince the jury of mitigating factors to avoid the death penalty, citing a traumatic brain injury Sierra suffered as a child, which allegedly altered his personality and cognitive abilities.
Life or Death Decision for Cuban Defendant
Sierra, a 42-year-old Cuban, pleaded guilty in August to nine counts, including first-degree murder, kidnapping, body abuse, and armed burglary, without a plea deal. The current phase is not to determine guilt, which Sierra has admitted, but to decide his punishment. The jury will recommend life imprisonment or the death penalty.
Under Florida's amended 2023 law, a death penalty recommendation requires only eight of 12 jurors to agree. Lead prosecutor Abbe Rifkin described the murders as "particularly heinous, atrocious, and cruel," while the defense hopes Sierra's brain injury and personal history will sway the jury to recommend a life sentence.
As of July 2026, according to the Death Penalty Information Center, five Cubans are on death row in Florida. If the jury...
Key Questions About the Miami Triple Murder Case
What triggered the triple murder committed by Alberto Sierra?
The murders were triggered by a jealousy-fueled argument between Sierra and his estranged wife, Gladys Machado, which escalated after he suspected her of infidelity.
What was Sierra's method for committing the murders?
Sierra used plastic bags to suffocate his victims, including his wife and her two daughters, as described in his confession to the authorities.
What is the defense's main argument to avoid the death penalty for Sierra?
The defense argues that Sierra suffered a traumatic brain injury during childhood, which they claim affected his personality and cognitive functions, serving as a mitigating factor against the death penalty.