The Epistemic Drift of Criminal Plea Agreements in Spain: From Oral Trial to a Structurally Biased Process

This paper analyzes the transformation of the Spanish plea bargaining system following Organic Law 1/2025 of January 2, which introduces measures to enhance the efficiency of the Public Justice Service. It examines how plea bargaining has evolved from a marginal mechanism in 1882 to become the dominant mode of criminal case resolution. The study identifies a fundamental distortion in criminal procedure: the preliminary investigation phase has effectively supplanted the oral trial, functioning as a de facto first instance court. This reality is sustained by three procedural trends: the exhaustive nature of preliminary investigations, the proliferation of pre-trial judicial decisions, and the gradual introduction of adversarial principles during the investigative phase. The paper demonstrates how cognitive biases inherent in criminal investigations and the uncritical adoption of police findings are transmitted directly into plea agreements without the corrective mechanisms provided by oral trials. This dynamic severely undermines the truth-seeking function of criminal justice and raises serious questions about the legitimacy of a system that has normalized the waiver of adversarial trials as standard practice.

Keywords
Plea bargaining; cognitive biases; presumption of innocence; negotiated justice