Lorenzetti was born in Rafaela, Santa Fe Province, the son of a primary school teacher and a travelling salesman. He studied at the Faculty of Juridical and Social Sciences of the National University of the Littoral, becoming a lawyer in 1978. At the time he counseled several labour unions. He obtained his doctorate in 1983, specializing in private law. Among his first interests was the civil liability of physicians in the exercise of their profession.
Besides his work as a lawyer during 26 years in his native city, he has taught in a number of law faculties around throughout the country. He has dictated hundreds of lectures and published more than 30 books in Argentina and abroad, as well as many articles in specialized publications. 
Appointed to the court by President Néstor Kirchner, and taking office on 12 December 2004, he filled the vacancy caused by the resignation of justice Adolfo Vázquez, and was the fourth Supreme Court justice to be appointed by President Kirchner since 2003. On 7 November 2006 he was appointed president of the Supreme Court by unanimous vote of his fellow justices, effective since 1 January 2007. His designation was approved by the Argentine Senate with only one vote against, and two abstentions.
Lorenzetti has expressed his view that the Supreme Court should be reduced to seven members, which is the current number (there should be nine, but two seats have been left vacant), since "there must be a true division of powers, which means that the members of the Court should be a number that is independent from the appointments made by a single president." 
A statement by UCR figure and former Mar del Plata Mayor Daniel Katz in support of a potential spot for Lorenzetti as Julio Cobos's running mate in the 2011 presidential election led to friction with the administration of President Cristina Kirchner, whose Cabinet Chief, Aníbal Fernández, expressed disapproval at Lorenzetti's silence on the issue.
On 23 June 2013, Lorenzetti claimed that he was being threatened and extorted by AFIP President Ricardo Echegaray. Lorenzetti claims the intimidation was in response to his verdicts against the constitutionality of government legislation. AFIP has denied any such investigation.
- Clarín, 12 June 2005. Lorenzetti: "Sería bueno para Kirchner no nombrar más jueces en la Corte".
- ADC en la Corte.
- La Capital, 7 November 2006. Ricardo Lorenzetti, elegido presidente de la Corte Suprema de Justicia.
- Terra, 22 December 2004. Lorenzetti asumió como ministro de la Corte.
- UPI: Casa Rosada reclama desmentida del titular de la Suprema (Spanish)
- La Nacion, 23 June 2013. La Corte y el Gobierno, en su peor momento.
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