CODIS 20, the European Standard Set and India's NDIS Locus Standards

The 13 original CODIS core loci were: CSF1PO, FGA, TH01, TPOX, vWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, and D21S11. The FBI selected these loci on the basis of four criteria: (1) they were located on separate chromosomes or sufficiently far apart on the same chromosome to segregate independently, satisfying the statistical independence requirement for the product rule; (2) each locus had a heterozygosity exceeding 0.70 in the US population databases; (3) each locus had been profiled in multiple US population groups; and (4) each locus could be robustly co-amplified in multiplex PCR.

The CODIS database opened under the DNA Identification Act 1994. By 2017, CODIS held over 12 million offender profiles and over 600,000 forensic unknown profiles, and the system was processing around 80,000 new profiles per month from contributing US federal and state laboratories. The UK National DNA Database (NDNAD), established in 1995 under the Criminal Justice and Public Order Act 1994, initially used a different locus set (the SGM Plus loci, which shared several loci with CODIS but not all), which created early cross-border comparison complications that were eventually resolved through locus harmonisation.

Australian state and territory forensic laboratories built their own national index (the National Criminal Investigation DNA Database, NCIDD) on a locus set that overlapped substantially with CODIS. Canada's National DNA Data Bank (NDDB) used a closely aligned panel from its inception in 2000. The practical result was that international casework between the US, UK, Australia, and Canada was generally feasible at the major shared loci, but not at the loci unique to each jurisdiction's panel.

On 1 January 2017, the FBI expanded the CODIS core locus set from 13 to 20 loci. The seven new loci added were D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433, and D22S1045. The selection of these particular loci was deliberate: all seven were already included in the European Standard Set (ESS), meaning the expansion dramatically improved compatibility between US CODIS and EU ESS databases at the technical level.

The expansion was driven by three convergent pressures. First, the adventitious match rate in a database of over 13 million profiles had grown to a statistically non-trivial level at 13 loci. A 13-locus random match probability in the US Caucasian population is of the order of 1 in 10 billion; at 20 loci it is of the order of 1 in 10 quintillion, reducing the likelihood of a false positive database hit to a negligible level for all practical purposes. Second, the international forensic community had been advocating for US-EU locus harmonisation since at least 2004 through the ENFSI DNA Working Group and INTERPOL's DNA Monitoring Expert Group. Third, new kit chemistries from Applied Biosystems (GlobalFiler, Investigator 24plex QS) and Promega (PowerPlex Fusion) were already running 21-24 loci routinely, making the practical cost of adding loci to the reference standard minimal.

The transition imposed a compliance requirement on all US CODIS-contributing laboratories: profiles submitted to NDIS after 1 January 2017 had to include all 20 core loci. The FBI provided a two-year grace period for validation and re-profiling of existing reference samples in state databases. DNA kit manufacturers completed validation studies and submitted the new kits to the FBI's DNA Mixture Interpretation Validation Program. UK laboratories, whose existing kits already included many of the new CODIS 20 loci as part of the ESS, required less extensive re-validation but updated their population frequency databases to include the new loci.

The European Standard Set of DNA loci was first defined by EDNAP (the European DNA Profiling Group) in 1992 as a seven-locus set for the purpose of cross-border comparison between European forensic DNA databases. The set expanded to twelve loci in 1997 (the ESS12), then to fifteen loci (ESS15) in 2009, and to the current seventeen-locus set (ESS17) formalised in 2012. ESS17 consists of: D3S1358, vWA, D16S539, D2S1338, D8S1179, D21S11, D18S51, D19S433, TH01, FGA, D22S1045, D5S818, D13S317, D7S820, SE33, D10S1248, and D1S1656, plus amelogenin.

SE33 (also designated ACTBP2) is the most notable locus unique to the European set. It is among the most polymorphic autosomal STR loci known, with over 90 alleles documented in population databases. This extreme polymorphism makes it particularly valuable for the discrimination of profiles that share alleles at all other loci. However, SE33 amplifies more variably than the CODIS loci and has a known high stutter rate, requiring laboratories to apply higher stutter thresholds.

The legal framework for cross-border DNA comparison within the EU is the Prüm Decisions (Council Decisions 2008/615/JHA and 2008/616/JHA), which obligate member states to make their national DNA database available for automated cross-border comparison. The Prüm framework uses a hit/no-hit system: a request from Germany to the Belgian national database does not transfer profile data directly but returns a yes/no result. A positive match then triggers a data-exchange request under bilateral legal instruments. As of 2023, twenty-six EU member states plus Norway, Iceland, Switzerland, and (until January 2021) the United Kingdom were participating in Prüm exchange using ESS-compatible profiles.

India does not yet have an operational national DNA database in the statutory sense, though profiling activity takes place across seventeen Central Forensic Science Laboratories (CFSLs) and numerous State FSLs. The DNA Technology (Use and Application) Regulation Bill 2019 proposed the creation of a National DNA Data Bank (NDDB) under the Central Government, with a National DNA Index System (NDIS) analogous to the US NDIS. The Bill passed the Lok Sabha on 9 September 2019 but lapsed when the 17th Lok Sabha dissolved before Rajya Sabha consideration. As of 2024, a revised draft remains under consideration by the Parliamentary Standing Committee on Science and Technology.

The proposed locus panel in the 2019 Bill's regulatory framework closely mirrors the CODIS 20 loci. The draft regulations referenced loci including D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820, D16S539, TH01, TPOX, CSF1PO, D2S1338, D19S433, and amelogenin, effectively the original CODIS 13 plus several of the 2017 expansion loci. D1S1656, D2S441, D10S1248, D12S391, and D22S1045 have been discussed in technical consultations as candidates for the Indian panel; their inclusion would bring the India NDIS to near-complete CODIS 20 compatibility.

The practical importance of the panel choice extends to INTERPOL casework. India participates in INTERPOL's I-24/7 communication network and its Notices system. The INTERPOL DNA database, maintained at the General Secretariat in Lyon, uses a 17-locus ESS-compatible profile. For Indian laboratory profiles to be submitted to or compared against the INTERPOL database, they must include the ESS core loci, for the statistical weight behind each database hit, see random match probability and the likelihood ratio, which all proposed India NDIS panels do include. The 2023 Interpol DNA Monitoring Expert Group meeting in Singapore noted that India, Bangladesh, Pakistan, and Sri Lanka have all expressed intent to join the INTERPOL DNA Gateway exchange mechanism once national databases are operational.

INTERPOL manages the global layer of DNA database cooperation through its DNA Gateway, a secure server hosted at the General Secretariat in Lyon. As of 2023, fifty-nine member countries contribute profiles to the INTERPOL DNA database. The exchange protocol uses INTERPOL's FIND (Forensic Information Network for DNA) system, and profiles are compared using a defined minimum set of loci that all contributing databases must include. This minimum set is substantially the ESS core, making ESS the de facto global common denominator.

The operational casework impact is significant. Profiles recovered from crime scenes in one jurisdiction are routinely checked against both domestic databases and the INTERPOL database. The Prüm cross-border network handles most intra-EU comparisons automatically; INTERPOL handles comparisons between non-EU countries and between EU and non-EU partners. A notable recent example is the cross-border identification work following the 2015-2016 Paris and Brussels terrorist attacks, where DNA profiles from recovered items were compared against profiles from suspects held in multiple national databases, and the INTERPOL profile comparison was used to confirm identities across jurisdictions that did not have bilateral data-sharing agreements.

For Indian casework, INTERPOL comparisons currently operate on an ad hoc basis through the CBI's Interpol National Central Bureau (NCB) in New Delhi, which submits profiles as criminal intelligence requests rather than through an automated database search. Once an Indian NDIS is operational and connected to the INTERPOL gateway, this process would move from case-by-case manual requests to automated hit/no-hit searching, substantially improving turnaround time on international cases.