After the Webinar: Introduction to Latent Prints. Q&A with Andrew Reitnauer

Webinar presenter Andrew Reitnauer answered a number of your questions after his presentation, Introduction to Latent Prints. Here are some of his responses.


Audience Question:  What would be the best next step for someone who wants to get into fingerprint analysis as a profession?

Andrew Reitnauer: We always want to continue the evolution of this science – because it is continuously evolving. One thing I always recommend is in this field you really have to get involved. There's a much smaller number of open positions available than there are collegiate graduates. To make yourself a marketable candidate, I highly recommend joining forensic organizations, depending on the actual discipline you're looking at, there are lots of large-scale organizations. With what we're talking about now, the science of fingerprints, the main organization would be the International Association for Identification (IAI). On their website, depending on where you live, there are numbers of regional divisions also available. Cost is always an option for people, depending especially for newly graduated students because tuition concerns can stay with you for a while. In joining those organizations, you're exposed to different practitioners, start networking. There's always training available, there are regional division conferences. There are also things like what we're doing today, online training, especially if it's a low cost or no-cost, is always a very good idea. A lot of companies or organizations may also have things on-demand or opportunities for you to partake and train in your own schedule – that's a wonderful opportunity as well, where there are previously recorded webinars or programs that you can register for. In doing that, you're able to start building those qualifications and your resume, making yourself a more marketable candidate.



Audience Question:  Can luminol be used to detect fingerprints or is this solution only used to detect blood? Can luminol actually destroy fingerprints?

Andrew Reitnauer:  Luminol is actually not something that you would use to develop any impression evidence. It is a screening tool to look for hidden or latent bloodstains that may be present. One of the reasons it can be used is through the actual application process itself, it is a very viscous liquid and it will start to mask all those individual characteristics. In terms of looking for cleanup, spatter that may be present, luminol will certainly help, same with BlueStar. Those two formulas are not what you would use to develop bloody impressions in terms of fingerprints, palm prints, because it would mask those individual characteristics. On scene, you can use a variety of blood reagents, some of the ones I've used is Amido Black, Leucocrystal Violet, Hungarian Red, Acid Yellow 7, and Phloxine B. They all have different visualization techniques. Some are readily visible with regular white light, Acid Yellow 7 is a fluorescent technique and Phloxine B when you shine an Oblique light on it, it reflects a silver color. In terms of blood reagents on the scene or even on evidence, you always want to choose your development technique that will give the greatest contrast. It one of those real fine qualitative characteristics really start to pop out.



Audience Question:  In your experience, which method of preserving fingerprints is better? Lifting the fingerprints and placing it on a backing card or photographing the impression?

Andrew Reitnauer: I'm a huge proponent of photographing. I've had a number of occasions where after using traditional fingerprint powders, a lot of things can happen when you lift that print. You may bring up some of the item itself. If you develop on say, a CD, the label may come up with the tape because of the strong adhesive on fingerprint tape. You may start to bring up things like that. The particulates within the powders themselves can often leave spots and chunks and that can also mask the lift just a little bit. You never know what's going to happen. I would always photograph first if you're at a scene and you powder develop a print on a point of entry in a burglary, I would recommend photographing that first before you lift it, just because you don't know, that lift may not work, you may get bubbles, the tape could rip. It might lift the door, not the powder. Sometimes you only get one chance to do it. But if you photograph it, you haven't disturbed the original impression at all. Take that photograph and if it lifts great, wonderful, now you have two copies of that print that you can work with.



Audience Question:  What is the percentage of prints that have been lifted from cartridge cases? Do you know of any studies done on that?

Andrew Reitnauer: There's some new technology that came out recently examining developing prints on casings. In my career, I probably processed 5,000 to 7,000 fired cartridge cases and I've never developed a single ridge. One of the reasons for that is that during a discharge process there's just a tremendous heat element that comes out. It usually just obliterates all detail. The only times that I know of that people have actually gotten prints in casework from fired casings is if they're actually etched. I mean, when cartridges are handled during a loading process, those oils and residues on your finger will actually corrode the brass from the casing and it etches in the print. The heat's not necessarily going to impact that when it's fired but as for actual percentages, I'm not aware of any studies that are comprehensive enough to really give that kind of information, but I would estimate that it's really low.



Audience Question:  What is your perspective on the fact that there is no number of points that is needed for identification of fingerprints in the US? What are your thoughts on whether or not you think this should change? Is there a number of points that they should be looking for to classify a fingerprint as a match?

Andrew Reitnauer: There is no minimum number, it is up to the examiner themselves. That came from an IAI resolution and it was reaffirmed by another symposium back in the 90s. In essence, it was determined that there's no minimum number simply because of that qualitative-quantitative relationship. There's no scientific basis saying that a cluster of x number of points has any more weight than those same amounts of points that are spread out more. As the examiner, when you're looking at things from your subjective perspective using the training, knowledge and skills you have, plus when you consider the number of prints that you've looked at, you often can put some more weight on certain characteristics because of the uniqueness of their appearance. Things such as 4 bifurcations right next to each other, followed by another feature may hold a lot more weight in your decision making than 4 bifurcations spread out throughout the totality of your print. I don't think that the number of points is going to be a mandate but there is a lot of research being done on the statistical analysis of the conclusion making process. While we're not quite there yet there are some publications that have come out. There are some agencies and laboratories that are starting to implement these statistical analyses and probabilistic models. There isn't just quite enough there yet to make it acceptable industry-wide. When you think about the variables that can happen, the different placement of minutiae, within the fingerprint itself, the number of minutiae within the fingerprint, things such as distortion, spatial relationship, things like that, there's a lot of variables that have to be considered. Post National Academy of Sciences report in 2008, Post-PCAST's in 2016, there's a lot of call for additional research in this field which is a wonderful thing. I know this is one of the topics that's being addressed it's just a very large-scale project that needs to be addressed.



Audience Question: Do anti-bacterial wipes reduce the presence of oils in fingerprints and thereby result in reduced latent fingerprints?

Andrew Reitnauer:  It can have a negative effect on the retention of those residues. Simply cleaning your skin, the presence of the alcohols that are present will actually start to evaporate the water component which is why a lot of times if you use those anti-bacterial gels or wipes, your skin will end up feeling kind of dry. It certainly can remove some of those contaminants it may also leave some contaminants on your hands. When you're talking about the residues that are present, they can be transferred from one surface to another, from your skin to the surface itself. It would probably have more of a negative impact that a positive impact. Anything that you put on your skin has the potential to become part of latent print residues.



Audience Question: Are smeared prints able to be reconstructed by an analyst?

Andrew Reitnauer:  It depends on the impression. There are a number of distortional factors that a trained and experienced examiner will be able to recognize and possibly work through those being lateral distortion or rotational distortion being kind of the bigger two. If you can understand the way that the actual friction ridge is structured, the movement that can happen when it comes into contact with a surface and what the resulting impression will be depending on the type of movement that occurs, you may be able to kind of reconstruct or work through with the distortion to get to the characteristics that are present. One thing that I always remember is in the examination process if I work through a very difficult impression and come to a conclusion, more chances than not, that conclusion must be verified by a second examiner. If there are ever concerns about if those features may actually be reliable because of the distortion factors that are present, those are obviously questions and consultations that will happen between examiners themselves. Often even overlapping prints because of the directionality of the friction ridges, they may crisscross each other, and you may be able to trace them through and follow them, and in essence, reconstruct the original configuration. 



Audience Question: Are there any guidelines or procedures that you can recommend for the prioritization of evidence for fingerprint examination? 

Andrew Reitnauer: Every laboratory's different, with their own backlogs and priority cases that come in, and own procedures to incorporate. In trying to address as many cases on the face as possible, two policies I've done previously that seem to work well, but we got to exclude the level one offenses – homicides, sexual assault, things of that nature. We'll take it to the lower offenses – robberies, burglaries, things like that. If you're able to identify one person in the case, you can shut down your examination, get those results to the detective on the case so that even if it turns out to be a victim or a legitimate access, at least that information has gone out to your investigators or legal counsel, so they can start to work on that information. In the meantime, you can address the next case in line and if that first case turns out more examinations are needed, or additional people are needed to be compared or something like that, you can always reopen and go back to it. But in the meantime, the next case in the queue has started the examination process and you're able to start to streamline some of your cases in order to serve your customers and clients best being the investigators in the process. Also, if cases are able to have multiple submissions in terms of the abundance of evidence, you may be able to find out there were 30 items collected at this assault. What are the most probative items that we can push out first? If there are 5 items of evidence waiting for processing, those can go through the lab first, those results can go out into the examination process and perhaps help the field investigators or case detectives in their investigation process whereas you can continue to work evidence but get some results on an expedited manner.


Click Here to See a Recording of "Introduction to Latent Prints."



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