Products of partial digestion with Hae III. Part 1. Characterization, casework experience and confirmation of the theory of three-, four- and five-banded RFLP pattern origins using partial digestion.

The sizes of Hae III partial digestion products at D1S7, D2S44, D4S139, D5S110, D10S28, and D17S26 were evaluated in experimentally generated partial digestions of liquid blood DNA. The partial digestion products were highly predictable, suggesting a very high level of sequence conservation in regions flanking variable number tandem repeat (VNTR) blocks. Partial digestion bands associated with three-or-more-banded patterns were also characterized. Partial digestion of three-banded patterns can be used to determine whether the extra bands arise due to internal Hae III sites in the VNTR block and to identify hidden three-banded patterns. Partial digestion products from forensic casework also conformed to size expectations. Presumed partial digestion bands from 27 forensic samples were compared to the experimentally generated data. The causes of partial digestion are examined and recommendations for interpreting forensic DNA evidence exhibiting partial digestion products are given.

Fixed-bin analysis for statistical evaluation of continuous distributions of allelic data from VNTR loci, for use in forensic comparisons.

The detection of DNA polymorphisms by RFLP analysis is having a major impact on identity testing in forensic science. At present, this approach is the best effort a forensic scientist can make to exclude an individual who has been falsely associated with an evidentiary sample found at a crime scene. When an analysis fails to exclude a suspect as a potential contributor of an evidentiary sample, a means should be provided to assess suitable weight to the putative match. Most important, the statistical analysis should not place undue weight on a genetic profile derived from an unknown sample that is attributed to an accused individual. The method must allow for limitations in conventional agarose-submarine-gel electrophoresis and Southern blotting procedure, limited sample population data, possible subpopulation differences, and potential sampling error. A conservative statistical method was developed based on arbitrarily defined fixed bins. This approach permits classification of continuous allelic data, provides for a simple and portable data-base system, and is unlikely to underestimate the frequency of occurrence of a set of alleles. This will help ensure that undue weight is not placed on a sample attributed to an accused individual.