The Office of Justice Programs Convicted Offender
DNA Sample Backlog Reduction Grant Program

Report No. 02-20
May 2002
Office of the Inspector General


ASCLD/LAB: the American Society of Crime Laboratory Directors/Laboratory Accreditation Board is one of the organizations that provides accreditation for labs. The organization performs a thorough inspection of the laboratory before it grants accreditation.

Candidate Match: when the CODIS software identifies what appears to be a match between two or more profiles, that match is called a candidate match. The candidate, or potential match, must then be verified by looking at the match details (produced by the software on a "Match Report"). If the candidate match is verified, then it is treated as a true match and it is considered a hit. Candidate matches that are determined to not be real matches are more common with the RFLP method than the STR method, since the STR method is more discriminating.

CODIS Administrator: the person at each laboratory that is responsible for the administration and security of the laboratory's CODIS. The position can also be referred to as CODIS Manager or CODIS Custodian. The CODIS Administrator is required by the QAS for each laboratory with a convicted offender database, although all CODIS labs should have someone filling that role.

Combined DNA Index System (CODIS): provides a framework for storing, maintaining, tracking, and searching DNA specimen information. CODIS refers to the entire system of DNA databases (convicted offender database, forensic database, victim database, etc.) maintained at the national, state, and local levels. CODIS currently consists of three distinct levels: the National DNA Index System, State DNA Index System, and Local DNA Index System.

Convicted Offender Database: consists of DNA records from persons who have been convicted in state or local courts of crimes that, according to state legislation, warrant inclusion in that state's convicted offender database.

DeoxyriboNucleic Acid (DNA): DNA is found in almost all living cells, and carries the encoded information necessary for building and maintaining life. This encoded information is what makes each person an individual. Human DNA consists of two strands of molecules that wrap around each other to resemble a twisted ladder whose sides are connected by rungs of chemicals called bases. There are four kinds of these chemical bases (also called nucleotides), and the order in which they are arranged is called the DNA sequence. It is this unique sequence that is determined when a DNA sample is typed.

DNA Profile: a set of DNA identification characteristics, i.e., the particular chemical base at the various DNA locations (loci), which permit the DNA of one person to be distinguishable from that of another person.

DNA Sample: a body tissue or fluid sample (blood, a buccal sample, or semen, for example) that can be subjected to DNA analysis.

Examiner (Analyst): an individual who conducts or directs the analysis of forensic casework samples, interprets data, and reaches conclusions. In other words, the analyst is the person performing the bulk of the DNA analysis work. The analyst's qualifications are governed by specific requirements as given in the QAS.

Hit: a confirmed match between two or more DNA profiles discovered by CODIS software at a single instant in time. In other words, a hit is a match between two or more profiles that the software finds when profiles are searched against each other. A hit can occur when an offender sample is matched to a sample from case evidence (forensic sample), when a forensic sample is matched against a forensic sample from another case, or a combination of these two.

Investigations Aided: the primary measuring unit that the FBI uses to quantify the success of CODIS. An investigation is aided when a DNA match through CODIS either identifies a potential suspect or links crimes together, but only when the DNA match provides new information that would not have been otherwise developed.

Loci: the plural form of locus.

Locus: a specific physical location on a chromosome. Analogous to an address for a house.

National DNA Index System (NDIS): the FBI-maintained national component to CODIS. NDIS contains DNA profiles uploaded from approved SDIS laboratories.

NFSTC: the National Forensic Science Technology Center provides certifications of compliance with the Quality Assurance Standards. The certifications are not the same as laboratory accreditation but are still used as an indication of compliance by various organizations.

Restriction Fragment Length Polymorphism Analysis (RFLP): a technique that uses probes to detect variation in a DNA sequence according to differences in the length of DNA fragments that are created using specific enzymes. These enzymes act like microscopic scalpels and cut the DNA strands at specific points, producing fragments that can be analyzed. The combination and number of base repeats within each particular sequence determine the size of the fragment and the differences among individuals. RFLP was used predominantly by DNA laboratories until newer technology was developed. This method can take as long as a couple of months to obtain results if radioactive agents are used. Also, a sizeable amount of good quality DNA is needed when using RFLP.

QAS: refers to the Quality Assurance Standards issued by the FBI Director upon the recommendation of the DNA Advisory Board. Quality Assurance refers to measures that are taken by labs to monitor, verify, and document performance. Two sets of QAS exist: QAS for Convicted Offender DNA Databasing Laboratories, effective April 1, 1999; and QAS for Forensic DNA Testing Laboratories, effective October 1, 1998.

SDIS: State DNA Index System containing the state-level DNA records uploaded from local laboratory sites within the state. SDIS is the state's repository of DNA identification records and is under the control of state authorities. The SDIS laboratory serves as the central point of contact for access to NDIS.

Short Tandem Repeat Analysis (STR): refers to a DNA typing method that utilizes a certain technology to quickly amplify and analyze sections of DNA that contain short tandem repeats. This method allows a high level of discrimination, since 13 loci (unique locations or identifiers) are examined and subsequently compared with other samples. STR also requires considerably less effort and less DNA than the RFLP technology. STR has been the standard typing method for crime-scene samples, and has been declared the typing method for all NDIS samples.