When a latent print is obtained from evidence of a crime it carries with it the potential to be compared to it’s possible source. This may be a victim, suspect, or another individual who came into contact with the object or scene itself whether it was during the crime or at some point in the past. Currently there are three broad conclusions that the latent print examiner will choose from as a result of the comparison: identification (the latent print was made by the subject being compared), exclusion (the subject compared is not the source), and inconclusive (the subject could neither be attributed as the source or excluded as the source). This last category seems to exist in a gray sea of indecisiveness however it not necessarily the case and often the inconclusive decision can easily be resolved with additional resources.
For now we’ll leave the undecided category for another time and focus on the quite common use of the inconclusive decision. Often, a latent print is deposited from a part of the finger or palm that is not sufficiently recorded on the exemplar (known fingerprint card recorded during an arrest or perhaps as is required for an application for a pistol permit; see above image) that the fingerprint examiner is asked to compare the latent print to. Sometimes even if the desired region is recorded on the exemplar/standard, it is of such poor quality that it cannot be used as needed for the comparison to the latent print. Unfortunately, it is not rare to have to rely upon exemplars that are of poorer quality than the latent print.
Take for example the three latent prints above that were produced by the tips of the fingers. These types of latent impressions are quite common when you consider just how often the tips of our fingers are used throughout the day. Chances are you’re using them right now to scroll through this on your smartphone. A typical fingerprint card has recordings of fingers that are rolled laterally from one side to the other and in doing so it is not likely to include the tip region of the fingers. Therefore, it’s not at all uncommon to come across latent prints that are of value for comparison but cannot be properly compared to the subject’s fingerprint card. Specially recorded prints including major case prints, which are an attempt to record all of the friction ridge skin (the skin responsible for leaving fingerprints behind) of the fingers and/or palms (see below) are required in order to be able to render a conclusive decision of either exclusion or identification. It may seem tedious to have to obtain all of these samples but it can go a long way in understanding whether an individual is the source (or not) of a particular latent print. So, it’s not necessarily “I don’t know” but more like, “I don’t know yet.”
SWGFAST (Scientific Working Group on Friction Ridge Analysis, Study, and Technology)
Document #10 Standards for Examining Friction Ridge Impressions and Resulting Conclusions (Latent/Tenprint)
An inconclusive conclusion resulting from a suitability decision as described in approach #1 in section 18.104.22.168.1 occurs when an examiner is unable to individualize or exclude due to an absence of complete and legible known prints (e.g., poor quality fingerprints and lack of comparable areas). In such an instance, the inconclusive conclusion means that the impression needs to be reexamined using clearly and completely recorded known impressions.