Fingerprints: The Science
1.0 What Are Fingerprints?
The fingers, palms and soles of the feet of humans—known as volar areas/volar surface—are characterized by friction ridges, which serve the biological purpose of aiding our ability to grasp, hold and climb . The development and appearance of friction ridges is not uniform—although they flow in concert with each other to form distinct patterns, they vary in length and width, branch off and end suddenly. Friction ridges form the patterns that we know as fingerprints.
At its most basic level, the rationale for fingerprinting is found in the empirical and anatomical knowledge that friction ridge skin is a) permanent, and b) unique. The validity of the first premise has been established by empirical observation as well as established knowledge of the anatomy and morphogenesis of friction ridge skin. The validity of the second premise, uniqueness, has so far been borne out by the manual expert inspection of millions of fingerprints. However, the underlying scientific or statistical basis of fingerprint individuality has not been yet rigorously studied or tested .
Friction ridges—a fingerprint
2.0 Basic Fingerprint Patterns
The three basic fingerprint patterns are the arch, the loop and the whorl. These major classes contain sub-category patterns. Arches, for example, can be either plain or tented. Loops can be either radial or ulnar. Whorls are the most complex of the fingerprint patterns and contain several sub-categories—central pocket, double loop and accidental . Loops are the most common pattern, followed by whorls and finally arches. Within these basic fingerprint patterns are a number of features called minutiae—the small and localized ridge characteristics that render each print unique .
Loops occur in about 60-65% of recorded fingerprint patterns. In a loop, one or more of the ridges curves in on itself, entering and terminating on the same side of the print. Loops can be either radial or ulnar. Radial loops are characterized by a loop pattern that flows towards the thumb. Ulnar loops are characterized by a loop pattern that flows toward the little finger. The classification of loops is based on the way the loops flow on the hand itself, not the print card. Ulnar loops are much more common than radial loops .
Ulnar on right, radial on left Ulnar on left, radial on right
Whorls are found in about 30-35% of recorded fingerprint patterns. In a whorl, some of the ridges make a turn through at least one circuit. The sub-classification of whorls is partially determined by the number of deltas found in the print, a delta being the point on a ridge that is found either on or near to the point of divergence of two lines. Further explanation of whorl classification is overly complex, but examples are shown below .
Arches are found in about 5% of recorded fingerprint patterns. The plain arch is characterized by a smooth flow of ridges that runs from one side to the other with a rise or wave in the center. Plain arches contain no significant “up thrusts”. The tented arch contains a “significant up thrust” in the ridges near the middle of the print, forcing the other ridges into a tent-like formation .
Minutiae are the points of interest or major features of a fingerprint. It is largely the minutiae of a print that render it unique, so they are used to make comparisons of one print with another. Common examples of minutiae include :
- ridge ending: the abrupt end of a ridge
- ridge bifurcation:a single ridge that divides into two ridges
- short ridge, or independent ridge: a ridge that commences, travels a short distance and then ends
- island: a single small ridge inside a short ridge or ridge ending that is not connected to all other ridges
- ridge enclosure: a single ridge that bifurcates and reunites shortly afterward to continue as a single ridge
- spur:a bifurcation with a short ridge branching off a longer ridge
- crossover or bridge: a short ridge that runs between two parallel ridges
- delta: a Y-shaped ridge meeting
- core: a U-turn in the ridge pattern .
3.0 Types of Collected Fingerprints
3.1 Inked Print
An inked print is the intentional and formal recording of the friction ridge patterns of an individual. Black printer’s ink is applied to the fingertips and then “stamped” or “rolled” onto a standard fingerprint card—in Canada, this card is called a C-216 form.
3.2 Patent Prints
A patent (or visible) print is one that does not require additional processing in order to be clearly recognizable as a fingerprint. An inked print taken by police would be a patent print, but in the context of a crime scene these prints are often made from the transfer of grease, motor oil, dirt or blood to a surface .
Fingerprints in blood (L) and dust (R)
3.3 Plastic Prints
A plastic print (also called an impressionor indentation print) is a recognizable fingerprint indentation made in a soft receiving surface, such as chewing gum, wax, sealant or a newly painted surface. These prints are have a three-dimensional character and, like patent prints, are immediately recognizable .
Fingerprint in gum (L) and paint (R)
3.4 Latent Prints
A latent print is invisible and, by definition, requires additional processing in order to be rendered visible and suitable for comparison. The processing for comparison is often called development, enhancement or visualization . Note, however, that modern forensic examiners often use the term “latent” to describe any accidental impression left by friction ridge skin on a surface, regardless of whether the print is visible or invisible. If invisible but suspected, investigators may use electronic, chemical or physical processing techniques to reveal the print.
True latent prints—invisible prints—are generally made from the natural sweat and oils present on the skin, although trace elements of other substances are likely included. Often, latent prints retrieved during investigation will include only a portion of the whole fingerprint. They may also be smudged, distorted or overlapped by other prints—it is important to note that print comparisons are not always made from “full” prints . The images below show the invisible latent prints developed from a firearm recovered in the course of investigation .
4.0 Methods of Collecting Fingerprints
The following is a review, not intended to be exhaustive, of some of the main procedures for collecting fingerprints.
4.1 Physical Methods
Traditionally, physical methods of collection are those that do not involve any chemicals or other reactions. The most common method is powder dusting, which has been in use for over a century. Powder dusting works by applying a fine powder to surfaces that may contain latent prints. The powder adheres to the residue left by the print—generally sweat and skin oils—and creates a contrast between the ridges and the background, revealing the pattern. The powder used is generally inorganic and can be found in several different colours. Black powder is the most common and yields the best results, unless the surface in question is too dark to yield an appropriate degree of contrast. In this case, coloured powders may be used .
To yield a print, examiners use specially constructed brushes to “dust” the powder across the surface in question. Commonly, these brushes are made with extremely lightweight fiberglass bristles, although they may also be made with feathers or animal hair . A variant of this simple brush-and-powder combination is the magnetic brush, known commercially as the Magna Brush™. The magnetic “brush” is actually a retractable magnet and is used in conjunction with special metallic magnetic powders . Like traditional powder dusting, the magnetic powder adheres to the sweat and oils of the print. The benefit of magnetic powder over traditional powder is that the excess powder is then removed using a magnetic wand that does not touch the print itself. This technique can be used on surfaces that would be unsuitable for traditional dusting, and is also less likely to damage the print, given that there is no contact .
Once the print is dusted, it must be “lifted”. This is done by carefully applying fingerprint tape to the print. When peeled off, the pattern—outlined by powder—sticks to the tape. The tape is then affixed to a stiff backing card, protecting and sealing the print. The print card is then labeled and initialed by the CSI who lifted it.
Inside a fingerprinting kit—image courtesy of www.forensics4fiction.com
A MagnaBrush™ magnetic brush
A traditional brush—the Zephyr™ Fiberglass Brush
Fingerprint lifting—image courtesy www.forensicssource.com
4.2 Chemical Methods
Iodine fuming is not actually a chemical reaction per se, as the iodine is not reacting with any of the components found in fingerprint residue. Instead, the natural fats and body oils in the residue temporarily absorb the iodine vapors, resulting in a colour change from clear to dark brown. Unless treated, the effect will fade with time, so the print is generally photographed and then allowed to fade. Although iodine fuming has been largely replaced by more modern methods, its main advantage is its non-destructive nature.
Fuming with an iodine fuming gun The brownish colour of a latent print developed with iodine fumes
Images courtesy of Lee Lofland, www.leelofland.com
Ninhydrin is a chemical used to detect the amino acids found in fingerprint residue. When ninhydrin comes in contact with these acids, it turns a deep blue or purple colour referred to as Ruhemann’s purple. Although ninhydrin is effective on many porous surfaces, it is most commonly used for developing latent prints found on paper. To develop the print, the document is sprayed with a ninhydrine solution and then allowed to dry. Development time can be hastened by the application of heat. As the ninhydrin reaction can fade over time, the developed prints, once revealed, are then photographed .
Ninhydrin & DFO pre-prepared solution. Image courtesy of Lee Lofland, www.leelofland.com
Latent prints on paper developed with ninhydrin.
DFO (1,8-Diazaflouren-9-one) is another chemical solution that reacts with the amino acids present in fingerprints. Like ninhydrin, it is most commonly used to find latent prints on porous surfaces. However, DFO does not cause an immediate colour change in the manner of ninhydrin—instead, it reacts with the amino acids to form fluorescent derivatives that glow under an Alternate Light Source (or ALS). ALS is a generic term used to describe any bright light source that can be configured with filters or slits to emit narrow-band light over a wide variety of different wavelength ranges .
(L) Pre-enhanced latent prints sprayed with DFO (R) same print after being lit by alternate light source.
Images courtesy of Patti Phillips, see www.leelofland.com
Cyanoacrylateis a generic name for a family of fast-acting adhesives. In the forensic community, it is commonly referred to as “Super Glue”. Cyanoacrylate is used to develop latent prints on a number of surfaces: plastics, electrical tape, garbage bags, Styrofoam, carbon paper, tin foil, wood, rubber, metals, cellophane, elastic bands and rocks. In order to develop latent prints using cyanoacrylate, the specimen containing the prints must be fumed. In the fuming process, the specimens or items on which latent prints are to be developed are placed into a fuming cabinet and suspended so as to expose all surfaces. Several drops of liquid cyanoacrylate are placed in dish in the cabinet. The items are then fumed until whitish-coloured fingerprint patterns appear. It is possible that the whitish colour will not provide sufficient contrast—if so the cyanoacrylate-developed print can be further enhanced by powder dusting .
(L) Fuming cabinet for cyanoacrylate (R) Cyanoacrylate “Super Glue”
Latent print developed by cyanoacrylate – image courtesy Department of Chemistry website, John Carroll University, see www.jcu.ed
Physical Developer (PD) is a silver-based aqueous reagent that reacts with the components of sebaceous sweat in latent prints to form a silver-gray deposit, outlining the ridge pattern. The “physical” part of the name, therefore, is a misnomer as PD is not a physical process like dusting, but rather a chemical one. It is used to develop latent fingerprints on most porous surfaces and some nonporous surfaces. PD is a destructive process, and so is always used last if at all. The process is expensive and complex and requires a great deal of experience on the part of the examiner. However, it is known to get results when no other methods work .
Adhesive Surface Techniques is a phrase used to describe four processing methods used to raise latent prints on sticky surfaces such as the adhesive side of sticky tapes, stick-on labels, peel-and-stick plastics etc. Three of the methods involve applying a thin paste onto the sticky surface in question and then washing it off. The paste only adheres to the print. The fourth method involves immersing the sticky surface in a gentian violet solution, which stains the print so it can be viewed and photographed in ordinary light .
5.0 Fingerprint Databases & Classification
In the past, before computers, police files of fingerprints were stored in the only possible form—hard copy. It became apparent to the pioneers of fingerprinting that some type of manageable, consistent classification system was necessary to make searching such files a reasonable and useful endeavour. To this end, a number of systems were developed. The most common of these was the Henry system, developed in the last 19th century by Sir Edward Henry . The Henry system allowed organized maintenance of the large files maintained by many law enforcement agencies, but searching manually for a single print was still close to impossible. Nevertheless, up until the 1990s all fingerprint examiners, identification personnel and many police officers were still receiving extensive training in classifying fingerprints using the Henry system .
However, while initially an extremely important aspect of forensic fingerprinting, the formal classification of prints has essentially been rendered useless by the age of computers and computer databases. Now, law enforcement rely on AFIS databases to automatically match unknown fingerprints, or even partial prints, against a massive database of known and unknown prints.
AFIS is an acronym for Automated Fingerprint Identification System, which is actually a generic term used to refer to any automated fingerprint identification system. In Canada, the RCMP operate a system called RAFIAS—the Regional Automated Fingerprint Identification Access System—which allows fingerprints taken from crime scenes or suspects to be submitted electronically and searched against the National Repository of Criminal Records. RAFIAS has been adopted by a number of police departments country-wide .
Contrary to the name, AFIS is not actually an “identification” system—rather, it is a searching system. Unlike on CSI, the computer cannot make the identification itself. Instead, it operates to narrow the number of possible candidates. Human fingerprint examiners make the final call .
The examiner or AFIS clerk begins by scanning an image of the fingerprint. Once it is uploaded, the software—which may differ between departments—allows the examiner to mark the locations of specific ridge characteristics. The examiner can narrow the search by adding data such as the gender of the suspect or which finger the print is from, if such information is known . The pattern type (i.e. arch, loop, whorl) may also be entered, as well as the location of the “core area” of the print. The markers make a type of “digital constellation” which the computer will compare against the patterns of prints already in the database . If the computer finds possible candidates for a match, it will return the results with a “score” from best to worst, based on how well the markers match between the unknown print and the search result . Some Canadian police departments are also adding palm prints to the database, as they are often found at crime scenes.
RTID is another important development in Canadian fingerprint technology. RTID, or Real Time Identification, is a National Police Service project run by the RCMP. It is designed to improve the efficiency of Canada’s national fingerprint repository; one of the main aims of the system to provide much faster service times .
A fingerprint entered into AFIS—the “markers” are highlighted in green In this case the probability of a match would be high.. Image courtesy of Spex Forensics, see www.spexforensics.com
6.0 The Four Premises of Fingerprint (Friction Ridge) Identification
The modern discipline of fingerprint identification is broken down into four fundamental premises, all of which arise from the scientific knowledge of the anatomy and structure of friction skin and friction ridge formation:
The four fundamental premises on which fingerprint identification is based are:
1) friction ridges first develop in the fetal stage, and reach their definitive form even before birth;
2) friction ridges remain permanent throughout the entire course of life, with the exception of distortions caused by scarring;
3) friction ridge patterns and the details found in small areas of friction ridges are unique and never repeated;
4) although each individual’s patterns are distinct in their ridge characteristics, their overall pattern appearances have similarities, allowing for systematic classification .
6.1 First Premise—Fingerprints Develop in Definitive Form Before Birth
The morphogenesis or cellular construction of friction ridge skin starts during the very first few weeks of gestation, with the fingers and volar pads appearing at approximately six or seven weeks. The ridges are visible by eleven weeks, but further development occurs throughout weeks eleven to twenty-four. By week twenty-four the development of the dermis is finalized and the physical blueprints for the final fingerprints of the child are complete and fairly permanent . The location and size of pore ducts and pore openings along the surface of friction ridge skin are also in their definitive form before birth and do not change .
6.2 Second Premise—Fingerprints Are Permanent
Once the “blueprint” of the fingerprint has been established in the stratum basale (generating layer) of the epidermis, it does not change except for injury, disease or decomposition after death. Disease or injury may affect the skin’s ability to regenerate, leading to the formation of scar tissue . Some “injuries” that affect fingerprints may not be obvious. Bricklayers, for example, wear down the ridges of their fingerprints by regularly handling heavy, rough materials. Something similar happens with people who work regularly with lime—a base chemical that can dissolve skin. However, if the activity stops, the skin will regenerate in the original pattern .
The persistency of friction skin is a result of the constant cycle of cellular morphogenesis, growth and migration that occurs throughout life. Cellular reproduction—or lack thereof—is also the reason that age may play a factor in the softening or blurring of friction ridges, as the elasticity of skin decreases with age, as does the rate of cellular growth. The ridges can become thicker, decreasing the height between the top of the ridge and the bottom of the furrow and reducing prominence. The prints of elderly people could therefore appear as smeared or smudged .
6.3 Third Premise—Fingerprint Patterns and Ridge Details are Unique
On the season premiere of the third season of “The Sopranos” Christopher Moltisanti, Tony Soprano’s strung-out nephew, ponders the claim that no two fingerprints are exactly alike. For scientists to know this, Christopher reasons, they would have to have everyone in the world together in one room to check. And not just everyone in the world right now, but also everyone who had ever lived, or ever would live. Realizing this is clearly impossible, Christopher concludes, “They got nothin’" . He is, of course, quite right. The claim that no two fingerprints are alike can never be proven absolutely. For this reason, the third premise of fingerprint identification has been subject to recent challenge. While the belief in fingerprint individuality has so far been borne out by the manual expert inspection of millions of fingerprints, the underlying scientific or statistical basis of fingerprint individuality has not been rigorously studied or tested .
Closely related people have a greater chance of having a similar genetic code that controls the appearance and development of the volar pads. This results in pattern characteristics that may appear to be passed from parent to child, but closer examination will reveal a significant number of differences. Even identical twins —who have the greatest likelihood of having the same genetic variations and experience the same physical variations during friction skin formation—do not have identical fingerprints. While in some cases the friction ridge patterns of twins are similar, in others they are not. Even though heredity may play a role in the appearance of the overall ridge configuration, it cannot and does not affect individual ridge unit alignment during growth. Ridge alignment, ridge shape, minutiae location and the location of the pore openings on the ridge unit all appear to occur randomly .
As said before, the belief in fingerprint individuality has so far been borne out by the manual expert inspection of millions of fingerprints. The sheer number of possible combinations of features on any given hand suggests that while two matching prints may not be impossible, it is certainly wildly improbable. Nevertheless, it is possible that a study of the frequency of various fingerprint characteristics could be used to determine the odds of two prints from different people matching. The math here would be very similar to that which supports the similar claim that “no two snowflakes are alike.” That statement is based on the fact that the sum total of possible variations of snowflakes is greater than the number that have fallen on earth, making it improbable to the point of impossible that two identical flakes have ever occurred .
6.4 Fourth Premise—The Unique Patterns of Friction Ridges Can be Classified
Although every fingerprint is believed to be unique, this knowledge would be useless without some means of classifying individual prints in order to allow for methodological and reasonably objective comparisons, as well as database searches.
Luckily fingerprints, while fundamentally unique, still share a sufficient degree of basic similarities in order to allow for classification. For example, prints can be classified by the basic patterns of loops, whorls and arches. Ridge details, on both fingertips and palms, can be classified by small level details such as islands, bifurcations and similar.
7.0 Fingerprint Comparison
In Canada, trained examiners always perform the fingerprint identifications made in the course of criminal investigations. Generally speaking, the examiner is comparing a developed latent print with inked prints from a known person or persons. In such cases, the first main issue is determining whether or not the latent print is suitable for identification purposes. The examiner must decide if the quality and quantity of the ridge detail in the latent print is sufficient to allow comparison with the known print. Once a latent print has been evaluated and found suitable for identification, it will be compared to known fingerprint cards. The known cards may be obtained through an AFIS search, or because the prints of a suspect are already on file . Once the examiner has a known print to compare the unknown to, the comparison process begins. In Canada, if the known prints are already in the system, they will be recorded on RCMP form C-216. Form C-216 contains the rolled and flat impressions of all ten fingers; the full name, date of birth and gender of the individual; the name and address of the police agency; the signature of the official who took the prints; and the reason the prints were requested .
7.1 The ACE-V Methodology of Comparison
Canadian police forces use the “ACE-V” methodology for fingerprint identification and comparison, with ACE-V being an acronym for “analysis”, “comparison”, “evaluation”—the formal process—followed by “verification.” David Ashbaugh, a former identification officer in the RCMP and internationally renowned fingerprinting expert, first introduced ACE-V in the 1980s. It has since become the most common method of fingerprint examination, both within Canada and globally . The purpose of the ACE-V methodology is to lend more structure and objectivity to the exercise of print comparison by embracing the factors required of a sound scientific practice. It is important to note that ACE-V is not a “points” system—there is no minimum or fixed number of corresponding details that must be found in order to make anidentification . Rather, it is a qualitative-quantitative analysis of the latent print and the known.
The ACE-V examination method proceeds as follows:
- The examiner must assess the unknown print to determine whether or not it is suitable for comparison. This involves the preliminary assessment of a number of factors .
- substrate distortio: the substrate is the material upon which the print was made. The examiner must ask: What is the condition of the substrate? Could it be causing any distortion in the print (i.e. creases on a plastic bag)
- matrix distortio: the matrix is the substance deposited by the print itself, i.e sweat and skin oils mixed with dirt. Could the substance of the print have caused distortion?
- development medium: all development mediums react with a specific material present in the latent print. This results in a change to its appearance. What change has occurred?
- transfer pressure distortion: has the print been distorted by the pressure of the individual’s hand, either downwards or sideways?
- anatomical factors: is it possible to determine which finger or hand deposited the print ?
- The examiner must describe how the unknown prints compare to the known. This is broken down into three basic levels of comparison
- First level: Assess the overall pattern of the friction ridges in both prints
- Second level: Assess the specific ridge formations in both print, including scars, creases etc
- Third level: Assess the intrinsic features of the friction ridges in both prints. Shapes, pore locations, scars, incipient ridges
- The examiner must ask
- Is there an agreement between the friction ridge formations present in the known and unknown prints?
- Is there a sufficient degree of shared uniqueness to characterize the donor of the known print as the only possible source of the unknown print? The examiner can make only one of the following three conclusions:
i) The two fingerprints originated from the same source—identification or individualization
ii) The fingerprint did not originate from the same source—non-identification or exclusion
iii) There is an insufficient degree of uniqueness to individualize, i.e. not similar enough to match but not different enough to eliminate—inconclusive .
NB: Qualified Conclusions (i.e. possible, probable or likely) are outside the acceptable limits of the science of friction ridge identifications. The conclusions reached by examiners must be absolute.
- If an identification is made, i.e. the examiner concludes that the two prints match, then his or her conclusion must be verified through peer review by another qualified fingerprint examiner. This serves to ensure that the objective scientific method is followed, and that the exercise of the examiner’s informed judgment was proper.
RCMP Form C-216 Magnifying glass used for human comparison of prints.
As of 2003, over 40 American courts have ruled uniformly that ACE-V is a valid method under the stringent Daubert requirements .
7.2 The “Minimum Points” Method
Early fingerprint experts devoted a great deal of time to the discussion of “points”, also known as minutiae, points of identity, points of interest, Galton points, points of similarity etc. All of these terms refer, in general, to ridge characteristics. Ridge characteristics are highly variable from person to person, finger to finger, and contribute significantly to the uniqueness of each fingerprint. A ridge characteristic, or “point”, could be a bifurcation, a ridge ending, a dot, an island etc. There are a great number of ridge characteristics in the average fingerprint—perhaps as many as 150. Prior to the adoption of the ACE-V methodology, the process of fingerprint comparison and the making of an identification were significantly lacking in the standards and objectivity required of a true science. There was also no formal verification process. In an attempt to address these quality control issues, a number of countries enacted legislation requiring that a certain number of “points” be identified in order to declare a match between known and unknown prints. Australia and France, for example, require at least twelve points of similarity; Italy and (formerly) the UK required sixteen; Brazil and Argentina require no less than thirty. The United States and Canada, on the other hand, employed no minimum standard at all .
However, under Ashbaugh’s ACE-V methodology there is no longer any requirement that an examiner meet a certain number of points in order to declare a match. Canada and the United States never had any legislation on this issue, but many of the countries that did are repealing it, including England, Wales, Scotland and Ireland . The confusion that persists in courtrooms is due largely to the ubiquity of the word “point”, which is still used as a synonym for “ridge characteristic”, and the prevalence of out of date forensic textbooks.
The abolishment of the “minimum points” system is made clear in statements from the forensic community:
1) The International Association for Identification (IAI) adopted in 1973 the findings of its Standardization Committee. This committee conducted a three-year research project into the question of establishing minimum standards for friction ridge characteristics. IAI Resolution #7 states the following:
"There is no valid scientific basis for requiring a minimum number of ridge characteristics which must be present in two fingerprints in order to establish positive identification."
2) The International Symposium on Fingerprint Detection and Identification meeting in Ne'urim, Israel in June 1995 established a consensus amongst delegates from 11 countries regarding the issue of "fixing" the number of points of identification. The "Ne'urim Declaration" states the following:
"No scientific basis exists for requiring that a pre-determined number of friction ridge features must be present in two impressions in order to establish a positive identification."
3) Under its 'Quality Assurance Guidelines for Latent Print Examiners' & ' Standards for Conclusion', SWGFAST (the Scientific Working Group on Friction Ridge Analysis, Study and Technology) addresses its criteria for Individualizations under Part I. Individualization; Section 1.2 Basic Principles: 1.2.1, and states the following:
"There is no scientific basis for requiring that a predetermined number of corresponding friction ridge details be present in two impressions in order to effect individualization."
8.0 Ridgeology & the Fingerprint Examiner as an Expert Witness
Ridgeology is a new term used to refer to the scientific study the friction ridges of the volar surfaces, and the qualitative-quantitative process of modern fingerprint identification. The term was coined by ex-RCMP officer and fingerprint expert David Ashbaugh, the originator of ACE-V. Like ACE-V, the discipline of “ridgeology” has attained international prominence and is commonly relied on in fingerprints comparisons all over the world. In Canada, ridgeology and the ACE-V method are practiced almost exclusively.
In many ways ridgeology is a response to the void left by the minimum points standard—while Ashbaugh does highlight ridge characteristics, he also advocates focusing on the general flow and shape the ridges themselves, the characteristics of the “edge” of the print and so on. However, Ashbaugh’s main goal with the discipline of ridgeology was to promote understanding of the actual science—anatomy, cellular morphogenesis, fetal development etc—that underlies the two main premise that support fingerprinting: permanence and uniqueness. With the advent of standardized methodology like ACE-V, Ashbaugh argues that it is not the procedure that is posing problems for fingerprinting—rather, it is the inability of fingerprint examiners to explain it . Ashbaugh states the problem on the very first page of his book, “While the ability to identify is inherent, an understanding of the process and the ability to describe it is not" . In Canada, we are far less likely to face this problem than other jurisdictions. Canadian police and identification officer training is more standardized than elsewhere, and considerably more demanding. Nevertheless, it is important for both the examiner and counsel to understand the science.
8.2 The Fingerprint Examiner as an Expert Witness
Despite the large-scale abandonment of the “points” method, fingerprint examiners are often faced with questions regarding the number of points the examiner requires to make an identification. If the examiner hesitates or refuses, he or she may be subjected to further questioning and accusations of incompetence or subjectivity. A poorly prepared examiner may become flustered to the point of giving a number that is arbitrary and meaningless . The best means of dealing with this is to ensure that the examiner is fully prepared to provide the court and counsel with a thorough explanation of all aspects underlying the modern discipline of fingerprinting and the means by which he or she made the identification in question . These are examples of areas that the fingerprint expert could face questions about in examination:
- The ACE-V comparison process and how it was used to identify the print in question
- Error rates—what are they and how are they determined?
- Proficiency training—how and when it was accomplished in the expert’s department. Results of expert’s proficiency test.
- Exact protocols followed when comparing latent prints and known prints
- The physiology of fingerprints, i.e. questions re: formation of sweat glands/friction ridges, the exact causes of differentiation, such as bone growth; skin cell replacement and its effect on friction ridges/the permanence of fingerprints
- The expert’s personal background—prepare CV with experience, training, research time, publications etc.
- Expert’s personnel record
- Have there been any disagreements with colleagues re: ID of latent print. Has the expert ever refused to verify another fingerprint examiner’s identification or has anyone ever refused to verify one of the expert’s?
- Ridge flow, characteristics, structure and how each one was or wasn’t taken into account in making the latent print ID
- The impact of possible print distortion; the medium in which the print was made (blood, dirt, sebaceous oils etc); and the substrate on which the print was deposited
- The operating principles of latent fingerprint development techniques, including fluorescent dye stains, lasers and alternate light sources .
9.1 Incorrect Identification—Brandon Mayfield
On March 11, 2004, three Madrid train stations were bombed, killing 191 people. The Spanish authorities lifted a fingerprint from a plastic bag of detonators, but were unable to find a match in their own databases. A digital copy of the latent print was sent to the FBI and run through iAFIS, resulting in a shortlist of possible matches. Upon human examination the print was declared a match to that of Brandon Mayfield, a lawyer from Oregon and recent Islamic convert. Mayfield’s fingerprints were on file from his time in the army, but his conversion to Islam and representation of an alleged terrorist had put him on the FBI radar several years before . Mayfield was immediately arrested. When the story of his arrest broke, news broadcasts quoted an unnamed US counterterrorism official as saying the fingerprints were an “absolutely incontrovertible match .
However, it was soon revealed that Spanish investigators had informed the FBI—prior to Mayfield’s arrest—that the fingerprints had been matched to an Algerian national living in Spain. Mayfield was released from custody and the FBI issued a statement alleging that a remarkable number of points of similarity appeared to exist between Mayfield’s prints and those of the bomber, but the identification of those points had been based on an image of substandard quality . The scandal intensified when unsealed court records revealed that the Spanish authorities had conveyed their doubt of the FBI conclusion weeks before Mayfield’s arrest. The records also showed that the FBI officials were so confident of a match they described as ''100 percent,'' that they failed to examine the original print while they were in Madrid to meet with the Spanish investigators . Mayfield spent seventeen days in FBI custody .
9.2 Incorrect Identification—Shirley McKie
Shirley McKie is a former Scottish police detective who was accused by the fingerprint analysis staff of the Scottish Criminal Record Office (SCRO) of leaving her thumbprint on the bathroom door frame of a murder crime scene. McKie denied having ever been in the house. The faith placed in the correctness of the identification was so great that Ms. McKie’s denial was seen as a lie, leading to her being first suspended, then fired, then arrested, tried and finally acquitted. The scandal grew amid allegations of misconduct on the part of the SCRO and the police. The case eventually led to a formal inquiry, which concluded that the misidentification had been a result of weaknesses in the methodology of fingerprint comparison, and that fingerprint examiners were ill equipped to explain their conclusions due to a lack of consideration for the limits of the discipline .
1 Robert E Gaensslen & Kimberly R Young, “Fingerprints” in Stuart H James & Jon J Nordby, eds, Forensic Science: An Introduction to Scientific and Investigative Techniques (Boca Raton FL: CRC Press) 341 at 342 [Gaensslen & Young].
2 Sharath Pankanti, Salil Prabhakar & Anil K Jain, “On the Individuality of Fingerprints” (2002) 24:8IEEE Transactions on Pattern Analysis and Machine Intelligence at 2.
5 Wisconsin Department of Justice, Crime Information Bureau Identification Manual, available online page 91
7 New Mexico Department of Health, Fingerprint Techniques Manual, online: <dhi.health.state.nm.us> at 8-10.
8 Davide Maltoni, Dario Maio, Anil K Jain & Salil Prabhakar, Handbook of Fingerprint Recognition (New York, NY: Springer-Verlag New York Inc, 2002) at p 85.
9 Ibid, all glossary terms.
10Gaensslen & Young at 349.
12 Gaensslen & Young, supra note 1 at 349.
14 Gaensslen & Young, supra note 1 at 350.
15 Campbell, supra note 10.
16 Gaensslen & Young, supra note 1 at 351.
17 Arrowhead Forensics, Latent Prints, Dusting Brushes and Applicators, online: .
18 Gaensslen & Young, supra note 1 at 352.
20 Pat A Wertheim, “Ninhydrin Processing” Crimes & Clues: The Art & Science of Criminal Investigation (December 1997), online: .
22 Henry C Lee & Robert Gaensslen, “Methods of Latent Print Development” in Henry C Lee & Robert Gaensslen, eds, Advances in Fingerprint Technology (Boca Raton, FL: CRC Press, 2001) 105 at 117-118 [Lee & Gaensslen].
23 Gareth Branwyn, “Forensics Lab 8.0: Revealing Latent Fingerprints – Introduction” Make Magazine (16 August 2009), online: .
25 Gaensslen & Young, supra note 1 at 346.
26 Gaensslen & Young, supra note 1 at 347.
27 Royal Canadian Mounted Police, “Regional Automated Fingerprint Access System” (8 August 2011), online: .
28 Tom Adair, “AFIS: The Automated Fingerprint Identification System” Forensics4Fiction (1 September 2011), online: [Adair].
32 Royal Canadian Mounted Police, “Real Time Identification Project” (8 August 2011), online: .
33 David Ashbaugh, Introduction to the Scientific Basis and Identification Process of Friction Ridge and Palmar Flexion Crease Identification, text from Ridgeology Consulting Services Forensic Ridgeology Course at 37 [Ashbaugh text].
34 Christophe Champod, Chris Lennard, Pierre Margot & Milutin Stoilovic, Fingerprints and Other Skin Impressions (Boca Raton FL: CRC Press LLC, 2004) at 9.
35 Ridges and Furrows, Friction Skin Growth, online
37 Katherine Harmon, “Can You Lose Your Fingerprints?” Scientific American (29 May 2009), online: .
39 Simon Cole, The Myth of Fingerprints (13 May 2001), online: The New York Times [Cole].
40 Sharath Pankanti, Salil Prabhakar & Anil K Jain, “On the Individuality of Fingerprints” (2002) 24:8IEEE Transactions on Pattern Analysis and Machine Intelligence at 2.
41 David Ashbaugh, “Ridgeology: Modern Evaluative Friction Ridge Identification” Royal Canadian Mounted Police—Forensic Identification Support Section (10 March 1999), pdf, online: <onin.com/fp/ridgeology.pdf> at 18 [Ashbaugh—Ridgeology].
42 John Roach, “‘No Two Snowflakes the Same’ Likely True, Research Reveals”, online: National Geographic
43 Gaensslen & Young, supra note 1 at 357.
44 Campbell, supra note 10.
45 Gaensslen & Young, supra note 33.
46 “Resolution 2009-18 ”International Association for Identification, online: .Resolution 2009-18, the amended version of the 1973 Resolution RESOLVED, the official position of the I.A.I., effective August 21, 2009, is as follows: “There currently exists no scientific basis for requiring a minimum amount of corresponding friction ridge detail information between two impressions to arrive at an opinion of single source attribution.”
47 Ridges & Furrows, The Friction Ridge Identification Process: AVE-V Worksheet, pdf online: ; Campbell, supra note 10.
52 L Haber & NH Haber, “Error Rates for Human Latent Print Examiners” NK Rathka, ed, Advances in Automatic Fingerprint Recognition, (New York: Springer Verlag, 2003).
53 United States v Llera Plaza, 188 F Supp (2d) 549 (2002) [Plaza].
54 I Evett & R Williams, “A Review of the Sixteen Point Fingerprint Standards in England and Wales” (1996) 46 Journal of Forensic Identiﬁcation 49. In 2000 England and Wales abolished the 16 point standard and identiﬁcations are based on the examiner’s judgment that there is a sufficient amount of corresponding ridge detail to justify the identiﬁcation
55 Ashbaugh—Ridgeology, supra note 52.
56 David Ashbaugh, Quantitative-Qualitative Friction Ridge Analysis: An Introducton to Basic and Advanced Ridgeology (Boca Ration, FL: CRC Press) at 1.
57 M Leanne Gray, Testifying to the Question of "Points", 55 Journal of Forensic Identification 165 (March 2005) [Gray].
58 Gary W Jones, “Are You Prepared?” FDIAI News, (April—June 2001), pdf, online: at 8,9.
60 David Heath & Hal Bernton, Portland Lawyer Released in Probe of Spain Bombings (21 May 2004), online: Seattle Times localnews/2001934919_mayfield21m.html> [Heath].
62 John Leyden, FBI Apology for Madrid Bomb Fingerprint Fiasco (26 May 2004), online: The Register [Leyden].
63 Sarah Kershaw & Eric Lichtblau. Spain had doubts before US help (26 May 2004), online: The New York Times .
64 Leyden, supra note 60.
65 “Background—About the Inquiry” The Fingerprint Inquiry of Scotland, online: .