Issues of bias in Forensic Science
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Transcript of Issues of bias in Forensic Science
ISSUES OF BIAS IN FORENSIC SCIENCE
Jeremy MorrisForensic Scientist
Johnson County (KS) Sheriff’s Office
What is “bias”? An inclination to present or hold a partial
perspective at the expense of (possibly equally valid) alternatives
Cognitive bias is the human tendency to make systematic decisions in certain circumstances based on mental processes rather than evidence
Making decisions based upon factors other than factual observations
Bias and science Utopian view of scientific conclusions is
that they will be unbiased
Simply not true. All scientists, even forensic scientists, have the potential for their exams to be affected by bias Not an ethical situation (i.e., desire for a
certain answer) Based on how our brain subconsciously makes
decisions
IABPA Code of Ethics “Bloodstain pattern analysis is rooted in the scientific
method and based on the application of scientific principles and techniques. The principle of objectivity is paramount in science, and its unwavering application in casework is essential. Being objective entails recognizing that bias may sometimes be unavoidable. Members should strive to recognize all biases which are present that could affect results and take all reasonable measures to ensure that these biases do not affect the results. Those measures may involve using certain protocols, designing experiments in a manner to counter or avoid the bias, or declining the assignment.”
Is this a problem? Yes – but knowing how big of a problem
or how often it occurs can’t readily be answered
We are most susceptible to bias when our observations or results are unclear or ambiguous. Our brain subconsciously seeks addition information to assist in the analysis
We can’t predict when this will happen or how often.
Problems with ambiguity
Context bias The manner in which information is
presented, or the environment in which the information is processed will have an affect upon how that information is perceived. Investigative context Severity of the crime External pressure Personal pressure Results of unrelated disciplines
Possible scenario Called to respond to a
likely murder-suicide involving husband and wife Told that neighbors have
heard lots of shouting lately
Told that husband has history of domestic abuseCan context bias cause an investigator to
adjust scene processing techniques?
Confirmation bias
The tendency to search for or interpret information in a way that confirms one’s preconceptions or favored theory and to steer clear of information that may disagree with those preconceptions or theory
Possible scenario Patent print found at
scene of homicide Value of print is borderline DNA of blood matches the
victim Victim’s blood found on the
suspect’s clothing During interrogation,
suspect apparently confesses
Can confirmation bias lean an analyst towards an identification?
Information What we have learned is that we can
never forget information. Once information or an idea has been planted in our head, it is impossible to forget it
This isn’t a problem we can “will” away
What do you see?
Abraham Lincoln and Mona Lisa
Forensic science and bias Nearly every other field of science has
implemented safeguards to minimize the effects of bias Double-blind studies in medicine Statistical analysis of data Have someone try and prove you wrong
Forensic science has only recently examined the ways in which our results can be affected by bias and how to minimize these effects
Some initial steps Make no assumptions Let the “mute witnesses” speak for
themselves Only get information that you actually
need Open up to being proved wrong
We don’t want this to happen
Questions?