Psychological Effects In Forensics

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I (1) In an ideal world of forensic science, human psychology, bias and subjectivity would not be issues of concern for analysts investigating crimes. As things are, however, the presence of the human element in forensic analysis can often introduce certain impediments to the integrity of an investigation, as well as raise questions as to the reliability of certain laboratory findings pertaining to crime cases as they are presented in the court of law. The “Context Effect” article discusses several such hindering psychological effects. The observer/context effect is one such perceptive error described as the context of a given situation having an effect on a person’s judgment in looking at the case. The observer effect ties in closely with context bias – in which an observer’s preconceived notions about a case will have an effect on its conclusion – and with the concept of expectancy. The latter effect, like many of the psychological effects discussed, can lead to devastating results, such as false convictions or worse. Expectancy effect (or the experimenter effect) happens when an analyst has an expectation for some result when running an assay, and this expectation in turn will impair the analyst’s judgment. The analyst might misinterpret results or even tweak the experiment so that results go in line with the expectation. (2) The Mayfield case goes to show how even FBI experts, top of the line investigators and analysts, can fall for these basic psychological effects. Expectancy effect is one of the most obvious effects in play here. Mayfield is an Islamist convert, and so it is very possible that the experts investigating the case incorrectly anticipated Mayfield as being the culprit due to his religious affiliation when his fingerprint match came up as a possibility. It is also possible that analysts engaged in what’s referred to as confirmation bias when
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