Skip to main content

Currently Skimming:

4 The Principles of Science and Interpreting Scientific Data
Pages 111-126

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 111...
... Adherence to scientific principles is important for concrete reasons: they enable the reliable inference of knowledge from uncertain information -- exactly the challenge faced by forensic scientists. Thus, the reliability of forensic science methods is greatly enhanced when those principles are followed.
From page 112...
... The process of sharing data and results requires careful recordkeeping, reviewed by others. In addition, the need for credibility among peers drives investigators to avoid conflicts of interest.
From page 113...
... Those data are then analyzed for any underlying patterns that may be useful in planning or interpreting tests that use the new method. In other situations, a process already has been formulated from existing experimental data, knowledge, and theory (e.g., "biological markers A, B, and C can be used in DNA forensic investigations to pair evidence with suspect")
From page 114...
... Thus, the relevant scientific community continues to check that established results still hold under new conditions and that they continue to hold in the face of new knowledge. The involvement of graduate student researchers in scientific research contributes greatly to this diligence, because part of their education is to read carefully and to question so-called established methods.
From page 115...
... bioforensics.com/conference04/TWGDAM/Quality_Assurance_Standards_2.pdf.   Paraphrased from Section 9 of the FBI's Quality Assurance Standards for Forensic DNA Testing Laboratories.
From page 116...
... A key task for the scientific investigator designing and conducting a scientific study, as well as for the analyst applying a scientific method to conduct a particular analysis, is to identify as many sources of error as possible, to control or to eliminate as many as possible, and to estimate the magnitude of remaining errors so that the conclusions drawn from the study are valid. Numerical data reported in a scientific paper include not just a single value (point estimate)
From page 117...
... , although quantification is possible. Error Rates Analyses in the forensic science disciplines are conducted to provide information for a variety of purposes in the criminal justice process.
From page 118...
... " As in the case of all analyses leading to classification conclusions (e.g., diagnostic tests in medicine) , the microscopic hair analysis process must be subjected to performance and validation studies in which appropriate error rates can be defined and estimated.
From page 119...
... The analyst is asked to determine, for each of the 200 samples, whether it does or does not come from a person in class C, and the true answer is known. The validation study returns the following results: Hypothetical Hair Analysis Validation Study Analysis of Hair Samples Indicates: Class C Not Class C Row Total Sample is from Class 95 5 100 C Persons True Positive (correct False Negative determination)
From page 120...
... The above four measures emphasize the ability of the analysis to make correct determinations. "Error rates" are defined as proportions of cases in which the analysis led to a false conclusion. For example, the complement of sensitivity (100 percent minus the sensitivity)
From page 121...
... , and the recognition of its limitations; and •  he conducting of validation studies of the performance of a foren t sic procedure to assess the percentages of false positives and false negatives. Clearly, better understanding of the measuring equipment and the measurement process leads to more improvements to every process and ultimately to fewer false positive and false negative results.
From page 122...
... Additional factors may play a role in analyses involving human interpretation, such as the experience, training, and inherent ability of the interpreter, the protocol for conducting the interpretation, and biases from a variety of sources, as discussed in the next section. The assessment of the accuracy of the conclusions from forensic analyses and the estimation of relevant error rates are key components of the mission of forensic science.
From page 123...
... For example, the instructions accompanying the latent prints included information such as the "suspect confessed to the crime" or the "suspect was in police custody at the time of the crime." In 6 of the 24 examinations that included contextual manipulation, the examiners reached conclusions that were consistent with the biasing information and different from the results they had reached when examining the same prints in their daily work.14 Other cognitive biases may be traced to common imperfections in our reasoning ability. One commonly recognized bias is the tendency to avoid cognitive dissonance, such as persuading oneself through rational argument that a purchase was a good value once the transaction is complete.
From page 124...
... Additionally, science seeks to publish its discoveries, findings, and conclusions so that they are subjected to independent peer review; this enables others to study biases that may exist in the investigative method or attempt to replicate unexpected results. Avoiding, or compensating for, a bias is an important task.
From page 125...
... The forensic science disciplines will profit enormously by full adoption of this scientific culture. CONCLUSION The way in which science is conducted is distinct from, and complementary to, other modes by which humans investigate and create.


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.