criminal-profiling-5
please address whether criminal profiling is effective? Please specify cases in which profiling was effective or when it misled an investigation. Make sure to include discussion on the benefits and drawbacks of criminal profiling. Include identification of the attributes of a successful criminal profiler and whether mental health professionals make good profilers?
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Different types of forensic data are used for forensic identification, primarily fingerprint and DNA evidence. Two samples are compared—samples taken from the suspect and trace evidence left at the crime scene. If the samples match, a source attribution can be made. Examiners determine whether a person should continue to be a suspect on the basis of sample similarity. If all other sources can be excluded, individuation has been achieved. The four ways an expert can use to communicate to a jury that forensic identification has been made are via (1) a qualitative statement (how strong the match is); (2) a simple match statement (the evidence is consistent with the suspect’s guilt); (3) a match plus statistics statement (the evidence is consistent with the suspect’s guilt, and we have the statistics to back up this finding); and (4) an individuation statement (the match perfectly identifies the suspect). Guidelines allow an expert giving testimony to provide only one of three conclusions—inconclusive results, exclusion of the suspect, or individuation.
Unfortunately, the narrowness of these guidelines can lead jurors to falsely believe that fingerprint evidence is absolute; for example, the jury has no information about possible false positive rates. For evidence to be scientifically meaningful, it should be reliable (consistent) and valid (measure what it says it is measuring). DNA evidence can be used to identify an individual by comparing the genetic profile found at the crime scene to that of a suspect. Sometimes there is a clear match, but when the DNA sample is incomplete, poorly collected, or poorly stored, the results can be ambiguous. This is why DNA evidence is usually accompanied by a probability statement (a random match probability) declaring how likely it is that the match occurred by chance.
A different, less objective type of evidence is fingerprints, whose patterns are described as a series of loops, whorls, and arches. Despite the popular culture claim that each person’s fingerprints are unique, no evidence exists to support this notion. In addition, the processes used to compare fingerprints from the crime scene (latent prints) to the suspect’s are not standardized. In addition, individual bias may corrupt the matching process if the examiner believes the prints are from a guilty suspect. Subjectivity also comes into play when bite marks or bullet striations are being compared. All of these comparative analyses require a known, captured, suspect or weapon for any comparisons to even be made.
Measures to eliminate some of the bias inherent in the matching process include proficiency testing and certification. In proficiency testing, analysts are given a sample (e.g., the suspect’s DNA and DNA from the crime scene that is not the victim’s). They then are asked to make a judgment whether there is a match. Because they cannot be biased by knowing the “suspect’s” identity, since the samples are also obtained from known individuals, it is relatively easy for laypeople like jurors to determine whether the experts’ statements are accurate or inaccurate. Still, when jurors are presented with DNA evidence, they tend to undervalue the accompanying probabilities, which causes them the place more faith in the evidence.