Skip to main content

Currently Skimming:

SUMMARY
Pages 1-26

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 1...
... By the summer of 1989, the scientific, legal, and forensic communities were calling for an examination of the issues by the National Research Council of the National Academy of Sciences. As a response, the Committee on DNA Technology in Forensic Science was formed; its first meeting was held in January 1990.
From page 2...
... c.~(ie-carrVln~ L}NA occurs in all (fells Em ll~V~ nucleus, including white blood cells, sperm, cells surrounding hair roots, and cells in saliva. These would be the cells of greatest interest in forensic studies.
From page 3...
... Except for identical twins, the DNA of a person is for practical purpos pair comes from the es unique. That is because one chromosome of each father and one from the mother; which chromosome of a given pair of a parent's chromosomes that parent contributes to the child is independent of which chromosome of another pair that parent gives to that child.
From page 4...
... Discriminating power for personal identification is achieved by using several usually at least foursingle-locus, multiallelic systems. The entire procedure for analyzing DNA with the RFLP method is diagrammed in Figure 2.
From page 5...
... The frequency of the combined genotype in the population is 0.42 x 0.01 x 0.32 x 0.02, or 0.000027, or approximately 1 in 37,000. That example illustrates what is called the product rule, or multiplication rule.
From page 6...
... TECHNICAL CONSIDERATIONS The forensic use of DNA typing is an outgrowth of its medical diagnostic use analysis of disease-causing genes based on comparison of a patient's DNA with that of family members to study inheritance patterns of genes or comparison with reference standards to detect mutations. To understand the challenges involved in such technology transfer, it is instruc tive to compare forensic DNA typing with DNA diagnostics.
From page 7...
... SUMMARY '' ~ Targeted sequence 0~ Cycle 1 ~_~1111111111llllllllllllllllllllllll ~ Cycle 2 Cycles 4 - 25 Unamplified DNA Denature and anneal primers Primer extension Denature and anneal primers Primer extension Denature and anneal primers Primer extension At least 105- fold increase in DNA FIGURE 3 Polymerase chain reaction (PCR)
From page 8...
... must be rigorously characterized in both research and forensic settings, to determine the circumstances under which it will yield reliable results. · DNA analysis in forensic science should be governed by the highest standards of scientific rigor, including the following requirements: Each DNA typing procedure must be completely described in a detailed, written laboratory protocol.
From page 9...
... (Because forensic science should avoid placing undue weight on incriminating evidence, an upper confidence limit of the frequency should be used in court.) If a particular DNA pattern occurred in 1 of 100 samples, the estimated frequency would be 1%, with an upper confidence limit of 4.7% If the pattern occurred in 0 of 100 samples, the estimated frequency would be 0%, with an upper confidence limit of 3%.
From page 10...
... Thus, in a recently reported analysis of the FBI databank, no exactly matching pairs were found in five-locus DNA profiles, and the closest match was a single three-locus match among 7.6 million pairwise comparisons.) The multiplication rule has been routinely applied to blood-group frequencies in the forensic setting.
From page 11...
... The validity of the multiplication rule depends on the assumption of absence of population substructure. Population substructure violates the assumption of statistical independence of alleles.
From page 12...
... Moreover, as pointed out earlier, pairwise comparisons of all five-locus DNA profiles in the FBI database showed no exact matches; the closest match was a single three-locus match among 7.6 million pairwise comparisons. Those studies are interpreted as indicating that multiplication of gene frequencies across loci does not lead to major inaccuracies in the calculation of genotype frequency at least not for the specific polymorphic loci examined.
From page 13...
... The committee is aware of the need to account for possible population substructure, and it recommends the use of the ceiling principle. The multiplication rule will yield conservative estimates even for a substructured population, provided that the allele frequencies used in the calculation exceed the allele frequencies in any of the population subgroups.
From page 14...
... The collection of samples and their study should be overseen by a National Committee on Forensic DNA Typing. · The ceiling principle should be used in applying the multiplication rule for estimating the frequency of particular DNA profiles.
From page 15...
... But it is now clear that DNA typing methods are a most powerful adjunct to forensic science for personal identification and have immense benefit to the public-so powerful, so complex, and so important that some degree of standardization of laboratory procedures is necessary to assure the courts of high-quality results. DNA typing is capable, in principle, of an extremely low inherent rate of false results, so the risk of error will come from poor laboratory
From page 16...
... . A comprehensive quality-assurance program must include elements that address education, training, and certification of personnel; specification and calibration of equipment and reagents; documentation and validation of analytical methods; use of appropriate standards and controls; sample handling procedures; proficiency testing; data interpretation and reporting; internal and external audits of all the above; and corrective actions to address deficiencies and weigh their importance for laboratory competence.
From page 17...
... Investigators could compare DNA profiles of biological evidence samples with profiles in a databank to search for suspects. In many respects, the situation is analogous to that of latent fingerprints.
From page 18...
... In contrast, the computer technology required for DNA databanks is relatively simple. Because DNA profiles can be reduced to a list of genetic types (hence, a list of numbers)
From page 19...
... · DNA profile databanks should be accessible only to legally authorized persons and should be stored in a secure information resource. · Legal policy concerning access and use of both DNA samples and DNA databank information should be established before widespread proliferation of samples and information repositories.
From page 20...
... · Private-sector firms should not be discouraged from continuing to prepare and analyze DNA samples for specific cases or for databank samples, but they must be held accountable for misuse and abuse to the same extent as government-funded laboratories and government authorities. DNA INFORMATION IN THE LEGAL SYSTEM To produce biological evidence that is admissible in court in criminal cases, forensic investigators must be well trained in the collection and handling of biological samples for DNA analysis.
From page 21...
... A majority of states profess adherence to the Frye rule, although a growing minority have adopted variations on the helpfulness standard suggested by the Federal Rules of Evidence. Frye predicates the admissibility of novel scientific evidence on its general acceptance in a particular scientific field: "While courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs." Thus, admissibility depends on the quality of the science underlying the evidence, as determined by scientists themselves.
From page 22...
... In determining admissibility according to the helpfulness standard under the Federal Rules of Evidence, without specifically repudiating the Frye rule, a court can adopt a more flexible approach. Rule 702 states that, "if scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or educa tion, may testify thereto in the form of an opinion or otherwise." Rule 702 should be read with Rule 403, which requires the court to determine the admissibility of evidence by balancing its probative force against its potential for misapplication by the jury.
From page 23...
... -Each person's DNA is unique (except that of identical twins) , although the actual discriminatory power of any particular DNA test will depend on the sites of DNA variation examined.
From page 24...
... The concerns are pertinent to the role of DNA technology in forensic science, as well as to its widespread use for other purposes and in other social contexts. A potential problem related to the confidentiality of any information obtained is the safeguarding of the information and the prevention of its unauthorized release or dissemination; that can also be classified under the heading of abuse and misuse, as well as seen as a violation of individual rights in the forensic context.
From page 25...
... As large felon databanks are created, the forensic community could well place more reliance on DNA evidence, and a possible consequence is the underplaying of other forensic evidence. Unwarranted expectations about the power of DNA technology might result in the neglect of relevant evidence.
From page 26...
... · Mechanisms should be established to ensure accountability of laboratories and personnel involved in DNA typing and to make appropriate public scrutiny possible. · Organizations that conduct accreditation or regulation of DNA technology for forensic purposes should not be subject to the influence of private companies, public laboratories, or other organizations actually engaged in laboratory work.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.