Realizing the Full Value of Latent Prints
By Martin W. "Marty" Collins
 California Identification Digest, March 1992

We are all aware of the strong evidential value of a print identification. Each of us could write a book on significant cases we have worked to successful conclusions. The importance and impact of positive print identifications is well documented and needs no further explanation. Yet there is another significant area of print comparison that is often totally disregarded and considered taboo by many in the latent print community. This is offering opinions on prints that lack the criteria for a positive identification.

Although every other discipline in forensic sciences commonly offers opinions that are less than positive, there is a hysterical reluctance among many latent print examiners to state any opinion other than the print is either a positive identification or it is of no value. One argument I've heard against offering a less than positive opinion in print identification is that the discipline should remain "pure". This would be the simple approach, to convince yourself that everything is either black or white but this philosophy is not in step with reality and that gray area in between is often too important to ignore. One examiner who uses 8 points to identify recently told me, if he had a bloody print in a murder case with 7 points that matched the suspect; he wouldn't even tell the detectives investigating the case about it. As far as he was concerned, the print didn't even exist if it didn't have 8 points. I hope this is just an isolated opinion and not a general practice in our discipline.

Let's talk about the criteria for making print identification. The biology of fingerprints is a science because of the accepted facts that friction ridges are formed prior to birth; they remain constant throughout life (barring injury etc.) and the arrangement of the ridge characteristics in any given area of friction skin is never duplicated. The comparison and identification of prints is more of an imprecise art or skill, with the expertise to interpret the marks left by the friction ridges being attained through years of training and experience. What constitutes and identification varies greatly between agencies and even between examiners in the same department. I just encountered an example of this where one examiner felt a print only possessed two or three matching characteristics and was no value; several examiners from another agency felt there were seven matching characteristics and the high probability of the print being made by a particular person existed, and examiners from a third agency reported the finding of ten matching ridge characteristics and a positive identification between the latent and the suspect's inked print. This example is not intended to be critical of any of the examiners in this case, but merely to demonstrate that the art of identifying prints is not a precise science. Once this fact is established, minds may be more receptive to allowing some latitude to those examiners who are willing to give an opinion on prints that have several matching points, but fall just short of the 100% positive identification.

Take the case where a latent print that possesses 8 matching points with a subject's inked print is compared by different examiners. The first examiner's criteria for identification is 8 points, so he makes a positive identification. The second examiner's criteria is 9 points, therefore he is unable to make a positive identification. Is it wrong for the second examiner to report his findings either verbally or in writing? Many examiners are adamant that the second examiner should report that since he did not make a positive identification, the print is of no value. I would argue that the facts of his examination, that he didn't make a positive identification, yet he found a significant number of matching points should be presented as evidence in both the investigation and prosecution of the case. Let the investigators, judges, and juries weigh the value of the evidence. How can we expect the courts to take us seriously when one examiner identifies a print and another reports the print is of no value?

Although discouraged, the Amended Resolution VII/V of the International Association for Identification allows for possible, probable or likely testimony with qualifiers. Wouldn't it be better practice to state the facts of a comparison (that the print lacked the criteria for a 100% positive identification, however, 6 (or 7) points match and there is a degree of probability the print was made by a particular person), rather than totally disregard the print or worse yet identify the print by lessening the criteria for an identification.

Those who insist on the fallacy that a print is either a positive identification or it is on no value, are encouraging practices that can lead to the worst possible scenario, the wrongful identification. Because many examiners feel pressured into positively identifying a print, misidentifications are made. Because wrongful identifications are usually not publicly documented, most people think bum identifications are a rare occurrence. Being a supervisor of a state agency, I have been asked by other agencies to arbitrate on many close and disputed prints. Unfortunately, too many prints are erroneously identified because examiners fee they had no option and they tried too hard to make an identification they could report.

In debates over this subject, the following hypothetical case has been used to point out the potential value of prints that lack the criteria for a positive identification. A print found at a murder scene has 6 clear characteristics and the ridge flow is discernable. There are several potential suspects and the matching of this print with any of the suspects would be crucial to the investigation and prosecution of the case. The six ridge characteristics, their unit relationship and ridge flow all correspond with one of the suspects and virtually nothing matches with the other suspects. Could you, with a clear conscience, testify this is of no value? To ignore this or simply state the print can be neither identified or eliminated is disregarding the facts and strong evidence in determining the guilt and innocence of the persons involved.

The above scenario is not always a hypothetical case. I have been involved in several cases that fit the criteria given above. When appropriate, members of my department, including myself, have testified to the probability of prints being made by or not being made by subjects, when the print lacked the criteria to be positively identified. There's no question this is often difficult testimony. However, when this type of testimony is elicited, it is because it is usually crucial to the case. I have found that as long as you are objective about the facts, your professional opinion as an expert is highly regarded by the courts. On two of these occasions, I had defense experts in the court monitoring my testimony. After I testified they acknowledged my testimony as being fair, objective, and that there was no reason for them to take the sand since they couldn't disagree with my findings.

Some examiners misunderstand resolution V. Being a Certified latent Print Examiner, I haven't found it difficult to stay within the established guidelines that state,
"Now therefore be it resolved that any member, officer or certified latent print examiner who initiates or volunteers oral or written reports or testimony of possible, probable or likely friction ridge identification, or who, when required in a judicial proceeding to provide such reports or testimony, does not qualify it with a statement that the print in question could be that of someone else, shall be deemed to be engaged in conduct unbecoming such member,.."

As I discussed writing a paper on this subject, I was pleasantly surprised by the support generated by my co-workers. A colleague of mine had obviously been thinking along the same lines and he submitted the following suggestion for comparison results. I wanted to list his name and give him credit for his suggestion, but he declined the recognition.


The statement is often made that there are only two possible results of a fingerprint vs. fingerprint or latent print vs. fingerprint comparison, the two prints either were or were not made by the same person. That might be the case, if both the known and the questioned prints always represented the same area of the finger or palm print; if both impressions were identifiable; if the ridge detail in each impression was of sufficient clarity; and if all examiners were of the same skill level.

Absent one or more of the above factors, the findings that a skilled examiner can make based upon a comparison in order to provide a full and complete statement of fact should go well beyond two possible outcomes. Following are some of the conclusions or findings that can be reached as a result of a comparison of an unknown impression (latent or inked) with a know impression:

A. Unidentifiable Unknown Impressions:

1. The unknown impression is of no value for identification or elimination purposes.
2. The unknown impression is of no identification value, however, subject X can be eliminated from having made the impression.
3. The unknown impression does not contain a sufficient number of ridge characteristics to be utilized for identification purposes. However all of the minutiae present in the unknown impression correspond with minutiae in the same area of the known impression of subject X, therefore subject X can neither be identified nor eliminated from having made the unknown impression.

B. Identifiable Impression:

1. The unknown impression was not made by subject X
2. The unknown impression was made by subject X
3. The unknown impression is identifiable, however, due to the poor quality of the known impressions, subject X can neither be eliminated nor identified as having made the unknown impression.
4. The unknown impression is identifiable, and although all of the minutiae that are visible in the area common to the two impressions match and no differing minutiae are present. An identification cannot be established due to the fact that a portion of the pertinent area of the known impression is not properly recorded (smudged, smeared, superimposed, or not recorded).

On previously listed section A-3, I might want to go a step further and be specific about the number of minutiae that match between the known and the unknown impressions. Section B-4 would be beneficial to investigators, because they could then take appropriate steps to obtain better sets of know prints for comparison. It would also be extremely helpful if the examiner indicated what area of the print the similarities were found.

I could list several cases where expert latent print testimony on non-identifiable prints helped the jury in making a more intelligent decision, however the hypothetical cases given in the paper should suffice in pointing out the value that can be gained by locating several points of similarity on a particular subject's prints. Usually when testimony is given on prints that are not identifiable, the examiner testifies to the number of matching points that are found and the prosecutor attempts to determine how high of a probability exists that the prints was made by a particular individual. I would like to share the results of one case that was somewhat different. A print on the alleged murder weapon possessed several ridge characteristics. One examiner testified that the print was not identifiable, therefore under Resolution V it was of no value. Another examiner compared the latent print with all areas of the major case prints of the suspect and determined the print was not made by the arrested subject. This case illustrates the value non-identifiable prints have to help eliminate subjects as well a pointing the investigation in their direction. Many of those familiar with this case consider this an example of good forensic practices by the examiner who eliminated the subject and question the ethics or ability of the examiner who testified the print was no value. Yet others criticized the examiner who eliminated the subject for giving his opinion and suggested he should have been reprimanded by I.A.I. Needless to say, emotions run high on this subject.

Constraints of time and manpower will not allow us to attempt to eliminate or find some similarities in every print we examine. However, every once in a while a crucial print that cannot be identified could be the deciding factor in determining guilt or innocence.

The other fields of Forensics are usually higher compensated in salary than latent prints. I firmly believe one reason for this is because they are compensated for their analytical skills, where in latent prints they somewhat jokingly imply you can be a latent print examiner if you can count to eight. Displaying analytical judgement raises our discipline to a higher degree of professionalism. Other disciplines in Forensics testify to the degrees of probability in their respective fields. Whey should the expert opinion of a Latent Print Examiner be limited or given any less consideration than an expert in serology, ballistics, trace evidence, impression evidence (tire and tool marks) or handwriting?