Idoia López Riaño was born on March 18, 1964, in San Sebastián, Spain. She led what appeared to be a stable childhood and education before becoming involved with the separatist group ETA. In 1984, at just 20 years old, she joined ETA—recruited by her boyfriend—and quickly became involved in plotting and executing political killings. Her beauty and charm earned her the nickname La Tigresa, and she developed a reputation for seducing police officers to extract information and plan lethal attacks.

At only 20, Riaño committed her first known political murder on November 16, 1984, when she, her boyfriend, and a third conspirator executed Joseph Couchot, accused by ETA of being a GAL member. Over the next two years, she participated in several high-profile attacks:
February 26, 1985 — Murdered Ángel Manuel Facal Soto
May 12, 1985 — Killed Police officer Máximo García Kleiner
June 17, 1986 — Involved in a triple assassination of military figures using a submachine gun
July 14, 1986 — Orchestrated a car bomb attack in Plaza República Dominicana, Madrid, killing 12 Guardia Civil. 

In total, she was charged with 23 murders between 1984 and 1986. Her tactics combined ruthless efficiency with calculated manipulation—attacks designed to shock political structures and sow terror.

On August 28, 1994, French authorities arrested Riaño in Aix-en-Provence alongside her partner. She served five years in France before being extradited to Spain on May 9, 2001. In 2002, she was convicted and sentenced to over 2,000 years in prison for her role in the ETA killings. During the trial, she defiantly declared her steadfast commitment to ETA's cause.

While imprisoned, she married twice (2004 and 2006), renounced violence through the “Vía Nanclares” approach, and publicly apologized—actions that led to her expulsion from ETA and eventual early release. Her conduct in prison and rehabilitation efforts contributed to parole. On June 13, 2017, after serving 23 years (one per victim), she was released. Her release generated significant media attention in Spain.