Levels Of Codis

The COmbined DNA Index System is composed of local, state, and national levels (Figure 18.1). All three levels contain the convicted offender and casework indexes and the population data file. The software is configurable to support any RFLP or PCR DNA markers although after 2000 only STR data is being added. At the local level or Local DNA Index System (LDIS), investigators can input their DNA profiles and search for matches with local cases. All forensic DNA records originate at the local level and are 'uploaded' or transmitted to the state and national levels.

Each participating state has a single laboratory that functions as the State DNA Index System (SDIS) to manage information at the state level. SDIS enables exchange and comparison of DNA profiles within a state and is usually operated by the agency responsible for maintaining a state's convicted offender DNA database program.

The National DNA Index System (NDIS) manages nationwide information in a single repository maintained by the FBI Laboratory. Participating states submit their DNA profiles in order to have searches performed on a national level. The role of NDIS is to search casework and offender indices, manage candidate matches, and return results of matches to the local LDIS level.

National Level

State Level

Local Level

National Level

State Level

Figure 18.1

Schematic of the three tiers in the Combined DNA Index System (CODIS). DNA profile information begins at the local level, or Local DNA Index System (LDIS), and then can be uploaded to the state level, or State DNA Index System (SDIS), and finally to the national level, or National DNA Index System (NDIS). Each local or state laboratory maintains its portion of CODIS while the FBI Laboratory maintains the national portion (NDIS).

When NDIS was first activated in October 1998, there were 119 000 offender profiles and 5000 forensic casework profiles from nine states. By December 1999, a little over a year later, 21 states and the FBI had inputted 211673 offender profiles and 11112 forensic profiles. While many of the original DNA profiles were from RFLP markers, forensic DNA laboratories in the United States have now converted completely to the 13 core STR loci. Presumably all samples for the foreseeable future will be typed with these STRs (Gill et al. 2004). In April 2004, the total number of offender STR profiles stood at more than 1.6 million with around 80 000 forensic profiles present in NDIS.

In order for a state to have its DNA profiles included in the national DNA index system, a memorandum of understanding must be signed whereby the state DNA laboratories agree to adhere to the FBI issued quality assurance standards that are listed in Appendix IV. A complete DNA profile of four RFLP markers or the 13 core STR loci is required for submission of convicted offender information to the National DNA Index System. There must also be a minimum number of loci included in the casework DNA profile: at least three CODIS RFLP loci or 10 of the 13 CODIS STR loci before uploading the information to NDIS. The lower number of loci needed for casework DNA profiles comes from recognition that degraded DNA samples obtained from forensic cases may not yield results at every marker even though analysis is attempted with those DNA markers (see Chapter 7).

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