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VALIDITY OF DNA EVIDENCE FOR HALAKHIC PURPOSES (PART 1)
I.THE NATURE OF DNA EVIDENCE
Deoxyribonucleic (DNA) testing is most often associated with attempts to identify criminal perpetrators or to exonerate persons accused of a crime. Identification by means of DNA is particularly useful in placing a suspect at the scene of a crime. Except for identical twins no two persons are known to possess identical DNA. In 1984 scientists developed a means of isolating DNA in a sample provided by a crime suspect or victim and comparing it with a sample recovered from a crime scene or from clothing worn by the suspect. Although the presence of DNA does not in itself conclusively prove the guilt of a suspect, it is a crucial factor in establishing guilt by means of circumstantial evidence.
DNA evidence is, logically speaking, most compelling in establishing paternity since a shared DNA profile constitutes extremely strong statistical evidence of a paternal-filial relationship. In paternity cases, a partial overlap of some DNA structures in different individuals is evidence that the persons compared had at least one common progenitor and hence are related.
Establishing a reliable DNA match is fraught with difficulty. One earlier commonly employed method in DNA testing is termed DNA fingerprinting or DNA profiling. The method involves a technique known as restriction fragment length polymorphism (RFLP) analysis in which long strands of DNA are extracted from body tissue and broken into fragments. Those fragments vary in length from person to person. If two samples contain fragments of different lengths they cannot have a common source. In order to reduce the likelihood that two people might each have a fragment of common length, a number of different fragments that have been discovered to be subject to a great degree of variability are measured. Those fragments are known as variable number tandem repeats (VNTRs). VNTRs of different lengths are presumed to have come from different individuals, Much as is the case with regard to fingerprints, VNTRs of equal length located at a similar position on a chromosome indicates that the two samples came from the same individual.1 RFLP of a minimum of six VNTRs yields profiles that are believed to be unique to each person. Acceptance of RFLP analysis relies upon...