INTRODUCTION

Public familiarity with forensic DNA analysis has grown considerably in recent years, in no small part thanks to television crime dramas in which investigators trace a perpetrator from a single strand of DNA left at a crime scene. Real casework is rarely so immediate, but genetic profiles recovered from crime-scene evidence remain among the most powerful tools available for linking an individual to a criminal event, whether by direct comparison with a known suspect or by searching a forensic DNA database when no suspect has yet been identified.

Since England and Wales established the first national forensic DNA database in 1995, more than 50 countries, including the United States with CODIS (1998), have built comparable systems, each shaped by its own legal, ethical and technical framework. Italy joined this international effort relatively late but comprehensively, ratifying the 2005 Prüm Treaty on cross-border police cooperation through Law No. 85 of 30 June 2009 [1, 2], and building a national system that is today among the most analytically rigorous in Europe. This article focuses on that Italian system: its legal and organizational structure, its day-to-day laboratory workflow, and research, development and validation activities supporting its analytical choices.

THE ITALIAN NATIONAL DNA DATABASE (BDN-DNA)

Legal and institutional framework

In 2005, Belgium, Germany, Spain, France, Luxembourg, the Netherlands and Austria signed the Prüm Treaty (also known as Schengen III) to strengthen cross-border cooperation against terrorism, organized crime and illegal immigration, providing for the exchange of fingerprint, DNA and vehicle-registration data [2]. Italy ratified the Treaty through Law No. 85 of 30 June 2009 [1], which established two structurally separate bodies with distinct roles defined by the legislator: the National DNA Database (BDN-DNA), housed at the Central Directorate of Criminal Police within the Ministry of the Interior, and the Central Laboratory for BDN-DNA, housed within the Department of Penitentiary Administration of the Ministry of Justice. The same law defined the procedures for sample collection, analysis, storage and international data exchange through CODIS. The National DNA Database has been operational since 2017, following the implementing regulation set out in Presidential Decree No. 87/2016 [3], while the Central Laboratory began operating in December 2017 after obtaining accreditation under UNI CEI EN ISO/IEC 17025:2018 [4].

Under Article 9 of Law No. 85/2009 [1], the Central Laboratory is the only laboratory in Italy authorized to produce and submit reference profiles of individuals stopped or arrested (following validation by the judicial authority) or convicted of non-negligent offences, completed or attempted, for which arrest in flagrante delicto is permitted. Certain categories are excluded from sampling, among them offences not typically characterized by violence or threat, offences against the administration of justice, forgery, and bankruptcy offences. Law enforcement agencies and ISO/IEC 17025:2018-accredited specialist laboratories, by contrast, populate BDN-DNA with unknown profiles obtained from crime-scene evidence, and the database also holds profiles of missing persons and their relatives.

Sample collection and chain of custody

DNA is collected exclusively through buccal swabbing and spotted on chemically treated cards that change colour upon contact with saliva; the types of cards that have been used for sampling, from the beginning of the collection to date, are Copan Nucleic-Card™ and FTA EasiCollect™. Sample collection is linked to the AFIS (Automated Fingerprint Identification System) database of the Central Identity Records Office, which generates a unique, pseudo-anonymized collection code for each subject. Two samples are collected from each subject, on the territory or within penitentiary institutions. The cards are then allowed to dry, packaged and labelled with the anonymized barcode before being sent to the Central Laboratory. Of the two cards, one is analysed to generate the DNA profile for the BDN-DNA (Figure 1), while the other is retained by the laboratory and kept available for the judicial authorities.

Database architecture and analytical requirements

BDN-DNA uses CODIS software as its storage and search platform, structured in two tiers, “local” and “national”, with only profiles typed for at least 10 loci accessible at the national level, enabling international exchange through Italy’s national contact point; mixed-source profiles are excluded from the national tier unless a clearly distinguishable major contributor can be identified. The database is searched systematically both between and within collections, to identify offenders, detect erroneously duplicated subject profiles, and link crime-scene profiles to one another.

Uniquely among forensic laboratories internationally, the Central Laboratory analyses every biological sample using two different, independently validated STR chemistries, requiring concordance across at least 10 autosomal loci before a profile is eligible for database entry, a stricter standard than most comparable systems worldwide. The Laboratory is also among the very few internationally to routinely upload Y-chromosome profiles of reference subjects alongside autosomal profiles, a valuable addition in cases involving sexual offences or DNA mixtures. Reference profiles produced by the Laboratory therefore comprise 26 autosomal and 28 Y-STR markers, substantially reducing the probability of adventitious or erroneous matches.

Profile and sample retention

DNA profiles are retained in BDN-DNA for 30 years, extended to 40 years for offences carrying mandatory arrest in flagrante delicto or in cases of recidivism; profiles are deleted at the end of this period or following acquittal. Biological samples are destroyed 8 years after collection.