Police have used fingerprint evidence to catch and convict criminals for more than 100 years. Specifically, latent fingerprint analysis is the method where an analyst compares an unknown fingerprint (latent print) recovered from some part of a crime scene, item, or other source and compares it to a known print. After comparing the known and unknown prints, the analyst then makes a determination as to whether the unknown print matches the known print, thereby leading to an identification.
Crime shows like NCIS and CSI have created misperceptions about the importance, collection and use of crime scene evidence, including fingerprints. Shows such as these stress the scientific nature of criminal investigations. They suggest that science (such as fingerprints) and the scientists who collect them are a dependable and accurate part of a criminal investigation. Further, these shows rarely depict any mistake or error being made by the “scientist”. As a result, jurors in real cases, see forensic evidence as an infallible and as a strong almost irrefutable evidence. However, not all forensic sciences are created equal, and the methodology behind fingerprint analysis is particularly problematic.
In September of 2016, the President’s Council of Advisors on Science and Technology (PCAST) published a report that set out a number of concerns regarding the methodologies behind latent print analysis. Regarding fingerprinting PCAST wrote, “[t]here are also nascent efforts to begin to move the field from a purely subjective method – although there is still a considerable way to go to achieve this important goal.” PCAST Report at 88. Plainly stated, fingerprint analysis a mostly a subjective not objective analysis – unlike other scientific evidence.
How does fingerprint examination work?
Everybody’s fingers and palms have “friction ridges” on them. These ridges occur in patterns (such as arches and loops) that contain specific features (for example, ridge endings and dots).
Fingerprint analysts use these patterns and features to compare an unknown (or “latent”) print with a known print, to determine if they may have come from the same person.
That said, given the general acceptance of fingerprint evidence, it is shocking how subjective fingerprint analysis really is, and even more shocking that a field that has been around since the 1800s is only now beginning to become objective. Latent print analysts uses the ACE or ACE-V method which consists of three or four steps: Analysis, Comparison, Evaluation, and Verification (optional) (YES – verification is optional!). At each stage purely subjective decisions are being made by the analyst. PCAST Report at 89-90.
In the Analysis step, an analyst examines the latent fingerprint, and they mark features of interest. When deciding what features to mark, the analyst has no standardized guidelines to follow. Instead, they simply choose what they think is a unique or identifiable feature. This could merely be a smudge, distortion, imperfection or something else. There are no standardized guidelines the analyst must follow in determining what “features” to note or how many features should be marked before the next stage of comparison, can proceed. Accordingly, an analyst could mark only one, two or six features and then attempt a comparison; it simply depends on the subjective choice of the analyst.
In the Comparison step, the analyst compares the known print to the latent print. During this step, the analyst uses the features previously marked on the latent print and attempts to compare them to the known print. This then leads to the Evaluation phase, which is when the analyst determines whether there is a match between the latent and known print.
The analyst’s final comparison and conclusion regarding the fingerprint is purely subjective. No standards exist that outline how many features must match, how close the match must be, or anything else. This means that even if an analyst sees differences between the latent and known print, they could still conclude based on their training and experience (and lacking any objective standards) that there was a match.
Once the evaluation is complete, there may or may not be a Verification step. This is the most difficult aspect of fingerprint analysis to understand - how can a purely subjective method NOT be verified? This is alone, demonstrates how fingerprint analysis does not follow the scientific method and therefore is it not credible science.
Problems with the underlying science
Until the mid-2000s, little scientific research had been done on most forensic disciplines, including fingerprinting. This lack of research became widely publicized in 2009, when the US National Research Council published a landmark report on the forensic sciences.
This report found that the only forensic method that had been rigorously validated was nuclear DNA analysis. All other forensic sciences – including fingerprinting – lacked a proper scientific foundation.
When examining this issue again in the 2016 PCAST report (discussed above) found that in the US only two properly designed studies of latent fingerprint analysis had been conducted. Both reports found the rate of false matches (known as “false positives”) to be very high: 1 in 18 and 1 in 30.
The main reasons for these high error rates is that fingerprint analysis involves human judgement and relies on the ACE-V methodology (discussed above) which is not sufficient to ensure the accuracy and reliability of an examiner’s conclusions. This means there is no guarantee that two different examiners who follow its steps will reach the same result. Again, this is counter to the principles of the scientific method.
The main reasons for these high error rates is that fingerprint analysis involves human judgement and relies on the ACE-V methodology (discussed above) which is not sufficient to ensure the accuracy and reliability of an examiner’s conclusions. This means there is no guarantee that two different examiners who follow its steps will reach the same result. Again, this is counter to the principles of the scientific method.
Because fingerprint analysis depends heavily on human judgement, an examiner’s conclusions may also be improperly influenced by non-scientific factors, such as irrelevant contextual information and cognitive bias. Another study found that fingerprint examiners can be improperly influenced by the use of automated fingerprint identification systems, which provide ordered lists of the most likely matches.
If you or a loved on has been charged with a crime hiring an experienced criminal defense attorney who is trained to attack sciences such as latent print analysis is vitally important. You should contact an experienced criminal defense attorney to talk about your case right away. At Jones Law Firm we have with decades of experience and can help. Contact us today to set up a free consultation. Please contact us by text or phone at (414) 774-6000 or email at laura@jlfwisconsin.com anytime.
*Any articles in the Libra or posted by Jones Law Firm LLC are not legal advice for a particular client or situation. Further no attorney-client relationship is intended or created with this post.*
