The Evaluation and Implementation of Match Criteria for Forensic Analysis of DNA

Abstract

This study describes a method for establishing match criteria used in forensic DNA typing. The validity of applying different match criteria based upon the molecular weight of a DNA band is discussed. The match criteria presented allow visually matching DNA patterns to be confirmed by computer assisted image analysis over the entire range of the sizing ladder. Approximately 5000 intragel and 5000 intergel comparisons were made between the restriction fragment length polymorphism (RFLP) DNA band sizes obtained from casework, mock cases, and environmentally insulted samples and the band sizes obtained from their corresponding bloodstain standards (controls). Analyses of these data suggested that fragments located in different molecular weight size regions of an analytical gel required different match criteria for assessing a visual match. The results of these analyses support the use of the following match criteria: Intragel 0.5–10 kb = ±1.7%, 10–15 kb = ±3.2%, 15–22.6 kb = ±5.8%; Intergel and blind control 0.5–10kb = ±3.0%, 10–15 kb = ±4.2%, 15–22.6 kb = ±10.0%; and human cell-line K562 and the monomorphic locus D7Z2 = ±2.5%. Each match criterion was also evaluated with respect to the distance in millimeters between matching bands throughout the 0.5–22.6 kb molecular weight size range. Applying these match criteria to different gel regions has been shown to be valid and reliable in comparisons conducted on more than 10,000 validation samples, in over 500 forensic cases and in more than 200 searches of a criminal sexual offender (CSO) database containing over 5000 individuals.

Guidelines for the validation and application of typing methods for use in bacterial epidemiology

“…Before a typing method may be used in a given situation, its appropriateness must have been clearly demonstrated. Every typing method therefore needs to be evaluated and validated with respect to a number of criteria [76–78]. These can be divided into performance and convenience criteria.…”

Graphical Tools for RFLP Measurement Quality Assurance: Single-Locus Charts

“…For these data, the x 1 interval extends from 6347 bp to 6607 bp and the x 2 interval extends from 3357 bp to 3494 bp. The choice of Ϯ2.0% of expected band size as a within-laboratory match window is in accord with recent experience-based recommendations (12). Again, this 2% match window has no simple probabilistic interpretation.…”

“…For K562 D4S139, the x 1 Ϯ 2.5% window extends from 6312 bp to 6636 bp and the x 2 Ϯ 2.5% window extends from 3352 bp to 3524 bp. The choice of Ϯ2.5% of expected band size as match window reflects common forensic practice (12). Since the expected among-laboratory measurement S is not simply proportional to band size, there is no simple probabilistic interpretation of any such percent-of-size criterion.…”

A computer simulation analysis of the accuracy of partial genome sequencing and restriction fragment analysis in estimating genetic relationships: an application to papillomavirus DNA sequences

“…The relationship between migration distances and fragment size may be affected by variation in gel density both between and within gels. There are also differences in measurement error between laboratories [25,26]. These deficiencies are accounted for by use of marker DNA fragments of known nucleotide base pair length to assist in estimating cleaved DNA fragment sizes; however, acknowledgement of remaining error of measurement of the size of detectable fragments is inherent in the application of a tolerance range for considering fragments of similar but different sizes as a "match" [27].…”