effects and bias in crime reconstruction

5

I. Observer Effects and Examiner Bias

Chisum and Turvey quote Paul L. Kirk, who was a pioneering criminalist, about the interpretation of evidence, “Physical evidence cannot be wrong, it cannot be perjured, it cannot be wholly absent. Only in its interpretation can there be error.” (Chisum, p. 51). This becomes a real issue because a great deal of the evidence we deal with can be interpreted in various ways depending on a number of subjective influences.

A. Observer Effects – Observer effects can be both conscious and subconscious. Both conscious and subconscious needs and expectations shape both our perception of facts and their interpretation. It can affect what is recognized as evidence, what is collected, what is examined, and how it is interpreted. At its most basic, an observer effect is a psychological bias or effect on the observer’s part that distorts how the evidence is recognized, collect, examined, or interpreted. It is often subconscious (below the level of awareness) on the part of the observer and may significantly affect the reconstruction of the crime. We all have them and the question thus becomes, not whether I have them, but how do I guard against them and eliminate their influence on my reconstruction.

B. Potential Observer Effects

1. Ambiguity and Subjectivity – Ambiguity is a factor when evidence or circumstances are incomplete, murky, or equivocal. Subjectivity is a factor when identifications and interpretations rest on the examiner’s experiences or beliefs. They become problematic when the examiner or investigator believes that his experience is all that is required to render an identification. There are at least three areas in reconstruction where subjectivity can show up: 1) evidence collection; 2) evidence quantity and quality; 3) lack of standards for qualifying the results of comparative analysis and identification (Chisum, p. 59). The occurrence of ambiguous physical evidence as well as evidence that is susceptible to subjective interpretation opens the way for subconscious observer effects to affect the results you obtain.

2. Lure of Expectation – We as investigators are often put in situations where we have access to information that can give rise to conscious or unconscious expectations. One of the most common expectations of this type is that the subject must be guilty of something even if they are not guilty of the crime of which they are accused. I once had another officer tell me (in reference to a real thug/scumbag that was a suspect in a homicide) that even if he had not done the crime, to charge him would not be a great miscarriage of justice. We work in a pro-prosecution environment where the suspect’s guilt is suspected and anticipated and this may lead to subconsciously developing pre-examination expectations that may influence the results (Chisum, p. 60).

3. Single Sample Testing – Evidence that is turned over to forensic examiners tends to fall into one of three catetories: 1) samples taken from the crime scene; 2) samples taken from the victim; 3) samples provided by the suspect (Chisum, p. 60). Single sample testing has been shown to directly affect whether an examiner’s report will associate the suspect’s with the crime scene or victim.

4. Prescreened Evidence – Even the best and most committed reconstructionist can be tripped up by having insufficient evidence. The problem with prescreened evidence occurs when the reconstructionist is given only a narrow amount of the physical evidence necessary to reach an informed conclusion. This prescreening of the evidence can come from anywhere – prosecuting attorneys, defense attorneys, superior officers, other investigators, etc. In fact, it can come from anyone who wants the reconstructionist to reach a particular outcome that the person providing the evidence favors. It is absolutely critical that we have access to all the evidence and information in a case, whether it appears relevant or not. That is the only way we can make an informed and unbiased interpretation.

5. Contradictory Findings – This can occur when you have more than one forensic expert involved in examining the same evidence. The problem arises when the evidence and interpretation are re-examined and one or more of the experts tailors his conclusions and interpretations so that they match the others.

6. Selective Re-examination – This can occur when there are contradictory findings and the prosecutor, defense attorney, or investigator pushes for a re-examination of the evidence by the expert whose conclusion is inconsistent with their preferred theory. The push is for them to re-examine the evidence and bring their findings into line with the findings of the other examiners.

C. Neutralizing Observer Effects and Examiner Bias – There are a number of reforms that can be put in place in forensic laboratories to help neutralize bias. These are beyond the scope of this course and our positions as investigators. The number one thing we can do as investigators is to be aware of the existence of observer effects, their subconscious nature, and their effect on how we perceive and interpret the evidence. I cannot emphasize enough that this requires an absolute commitment to truth and honesty, no matter the cost or where they lead. Be aware of your own biases (we all have them) and guard against them. Never fall in love with a theory and always be ready to modify or discard your theory when evidence contradicts it. You must have an absolute commitment to examining and understanding all of the information and evidence in the case and not just part of it.

II. Practice Standards Related to Crime Reconstruction – There are certain ethical standards that must be maintained in relation to crime reconstruction: (Chisum, pp. 116-123)

A. The reconstruction must diligently try to avoid bias;

B. All relevant evidence and information must be considered in order to perform and adequate reconstruction;

C. The reconstructionist must determine if the evidence is of sufficient quality to provide the basis for a reconstruction.

D. The reconstructionist must visit the crime scene in person;

E. The reconstructionist must make his conclusions and the basis for them in writing;

F. The reconstructionist must have an understanding of science, forensic science, and the scientific method;

G. The conclusions MUST be based on established facts – no fact may be assumed for the purpose of the analysis;

H. Any conclusions must be valid inferences based on logical arguments and analytical reasoning;

I. The conclusions must be made through the use of the scientific method – that is put the conclusions to the test; and

J. Any evidence, data, or findings on which the conclusions are based must be made available through presentation of the evidence itself or through citation of a source that can be examined by others.

Even though these standards technically apply to someone who is declared an expert in crime reconstruction, they also should apply to us as investigators as we try to reconstruct the crime through our investigations. The paramount idea is one that I have tried to practice in every investigation I have ever done – Seek the Total Truth and Follow It Wherever It May Lead!! As trite as it may sound, we are the finders of fact and it is up to others to determine guilt or innocence based on the facts we find. Therefore we can never afford to manipulate or shade the facts in any manner. We have to present the total facts – everything we know about the case to the triers of fact. I truly believe that homicide investigation is sacred trust that I can never violate except at great peril to everything I swore to protect. Enough said!

END OF READING

Chisum, W. Jerry and Brent E. Turvey. Crime Reconstruction. Amsterdam: Academic Press-Elsevier, 2007.