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 abuse

Can 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?