CLPEX Chat Board

VII. Exclusions
The general practice in the field of latent prints is that of "making an identification." Simply because no latent print of sufficient quality and quantity was found with features similar to the suspect does not mean that the suspect did not handle the evidence. Someone can handle an object and leave no latent print(s); therefore, practitioners espouse that no one can ever be excluded as having touched the evidence. In keeping with this philosophy, a latent print examiner tends to approach the comparison to "make an ident," rather than to attempt to exclude. This concept is similar to any other forensic analysis in that a lack of evidence does not necessarily exclude a suspect. However, it contrasts slightly with the doctrine of other forensic science disciplines. In forensic science examinations, regardless of the discipline, a pattern or profile (or some other data) is generated from the evidence, and it is compared with that obtained from a reference sample(s) in an attempt to exclude the two samples as having originated from the same source. When an examiner fails to exclude, then some significance is placed on that observation or finding. The more powerful or resolving the analysis, the more likely it is that wrongly associated samples will be excluded. The tremendous variability observed in friction ridge skin makes analysis of latent prints one of the most powerful exculpatory tools available to the forensic scientist. In fairness, an examiner does look for discrepancies in ridge detail that would result in an interpretation of exclusion. However, this approach is implemented only for prints deemed suitable for comparison.
In the first step of ACE-V, the examiner analyzes a latent print to determine if it is suitable for comparison. However, some prints may not meet this criterion, but they may provide exculpatory information. This can depend on how one frames the focus for exclusion. As stated above, no one can ever be excluded as handling the evidence because a person can touch an object and not leave a latent print. Alternatively, a defendant may desire to know if there are latent prints on the object demonstrating that someone else did handle the object.

An example may illustrate the point. Consider the recovery of a latent print on a glass found at a crime scene. The print is degraded such that the quality of Level II and Level III features is too poor to proceed to the comparison phase of the examination. The print is therefore declared "of no value" and discarded. No further work will be performed on this print. In this scenario, the Level I features clearly present the pattern of a whorl. Now assume that a suspect is apprehended and his or her fingerprints (and possibly other areas of friction ridge skin) have no whorls. In this case, even though it lacked sufficient quality or detail for an identification, the pattern would have excluded the suspect as the source of any prints found on the evidence. The defense and prosecution may want to know if the evidence revealed that someone other than the defendant handled the evidence. Exclusions are a very useful investigative tool and are currently underutilized.

The issue of exculpatory power of evidence is complex but needs further investigation. Some interviewees suggested to the committee that patterns insufficient for an identification could be artifactual. Thus false-positive and false-negative results could be obtained. This needs to be further studied and documented. It would not be wise to recommend a procedure that may have an inherently high error rate. There also is a tremendous resource consideration. If it were deemed reliable to proceed with the exculpatory model, then a substantially larger workforce (and concomitant resources) would be needed, case backlogs would increase, and more storage facilities would be required.

In this case, even though it lacked sufficient quality or detail for an identification, the pattern would have excluded the suspect as the source of any prints found on the evidence. The defense and prosecution may want to know if the evidence revealed that someone other than the defendant handled the evidence.

.......the pattern would have excluded the suspect as the source of the print found on the evidence..........

You should be a proof reader or on the editortial board.

Whatta yew chrge far prufreding. I gutta a latte.