José Ernesto Medellín Rojas was born on March 4, 1975, in Nuevo Laredo, Tamaulipas, Mexico. He moved to the United States as a child and grew up in Houston, Texas. Medellín became involved in gang activity at an early age, joining the "Black and White" gang, which was known for violent crimes, including assaults and robberies.

By his late teens, Medellín had a history of delinquency, spending much of his time with fellow gang members rather than pursuing an education or stable employment.

On the night of June 24, 1993, Medellín and other members of the "Black and White" gang gathered at T.C. Jester Park in Houston for a gang initiation. The group, which included Peter Cantu, Derrick O’Brien, Efrain Pérez, and two other members, spent the evening drinking and engaging in violent behavior.

At around 11:30 PM, 14-year-old Jennifer Ertman and 16-year-old Elizabeth Peña were walking home along a shortcut near the railroad tracks after visiting a friend. They crossed paths with Medellín and his gang, who decided to attack them. The girls were dragged into a secluded area, where they were repeatedly raped, beaten, and tortured for over an hour.

When the gang decided to kill them to eliminate witnesses, some members used shoelaces, others used a belt, and they stomped on the girls’ necks until they stopped breathing. The gang then bragged about the crime, with Medellín himself later telling a friend that it was “the most fun he ever had.” His brother, shocked by the confession, reported the crime to the police, leading to the gang's arrest.

Medellín was convicted of capital murder in 1994 and sentenced to death. His case gained international attention because, as a Mexican national, he was not informed of his right to consular assistance under the Vienna Convention. The Mexican government and international organizations, including the International Court of Justice and Amnesty International, advocated for a review of his case. Despite these appeals, the U.S. Supreme Court ruled that Texas had the right to proceed with his execution.

On August 5, 2008, José Ernesto Medellín was executed by lethal injection at the Texas State Penitentiary in Huntsville. In his final statement, he expressed remorse but did not directly address the victims' families. His execution marked the second carried out for the murders of Jennifer Ertman and Elizabeth Peña, following Derrick O'Brien's execution in 2006. The case remains one of the most infamous in Texas history, reinforcing the state's tough stance on capital punishment.