Editing Fingerprint (section)

== Capture and detection ==

=== Live scan devices ===
[[File:Fingerprint scanner identification.jpg|thumb|Fingerprint being scanned]]
[[File:3DFingerprint.jpg|thumb|3D fingerprint<ref name=3DPrintsweb>{{cite magazine
 | url = http://www.technologyreview.com/computing/23549/?a=f
 | title = Touchless 3-D Fingerprinting: A new system offers better speed and accuracy
 | magazine = Technology Review
 | first = Rachel
 | last = Kremen
 | date = September 2009
 | access-date = March 17, 2010
 | archive-date = October 20, 2009
 | archive-url = https://web.archive.org/web/20091020062002/http://www.technologyreview.com/computing/23549/?a=f
 | url-status = live
 }}</ref>]]

Fingerprint image acquisition is the most critical step in an automated fingerprint authentication system, as it determines the final fingerprint image quality, which has a drastic effect on the overall system performance. There are different types of fingerprint readers on the market, but the basic idea behind each is to measure the physical difference between ridges and valleys.

All the proposed methods can be grouped into two major families: solid-state fingerprint readers and optical fingerprint readers. The procedure for capturing a fingerprint using a sensor consists of rolling or touching with the finger onto a sensing area, which according to the physical principle in use (optical, ultrasonic, capacitive, or thermal{{spaced endash}}see {{section link||Fingerprint sensors}}) captures the difference between valleys and ridges. When a finger touches or rolls onto a surface, the elastic skin deforms. The quantity and direction of the pressure applied by the user, the skin conditions and the projection of an irregular 3D object (the finger) onto a 2D flat plane introduce distortions, noise, and inconsistencies in the captured fingerprint image. These problems result in inconsistent and non-uniform irregularities in the image.<ref name=2DPrintDeform>{{cite book | title = Estimating fingerprint deformation| author = Ross A. Jain| publisher = Proceedings of the International Conference on Biometric Authentication (ICBA)| year = 2004 }}</ref> During each acquisition, therefore, the results of the imaging are different and uncontrollable. The representation of the same fingerprint changes every time the finger is placed on the sensor plate, increasing the complexity of any attempt to match fingerprints, impairing the system performance and consequently, limiting the widespread use of this [[biometric]] technology.

In order to overcome these problems, as of 2010, non-contact or touchless 3D fingerprint scanners have been developed. Acquiring detailed 3D information, 3D fingerprint scanners take a digital approach to the analog process of pressing or rolling the finger. By modelling the distance between neighboring points, the fingerprint can be imaged at a resolution high enough to record all the necessary detail.<ref name=3DPrints>{{cite book |first = Yongchang |last = Wang |author2 = Q. Hao |author3 = A. Fatehpuria  |author4 = D. L. Lau |author5 = L. G. Hassebrook|title = 2009 First IEEE International Conference on Biometrics, Identity and Security (BIdS) |year  = 2009 |chapter = Data Acquisition and Quality Analysis of 3-Dimensional Fingerprints |pages = 1–9 |publisher = IEEE conference on Biometrics, Identity and Security |location = Florida|doi = 10.1109/BIDS.2009.5507527 |isbn = 978-1424452767 |s2cid = 519064 }}</ref>

=== Fingerprinting on cadavers ===
The human skin itself, which is a regenerating organ until death, and environmental factors such as lotions and cosmetics, pose challenges when fingerprinting a human. Following the death of a human, the skin dries and cools. Fingerprints of dead humans may be obtained during an [[autopsy]].<ref>{{Cite book|title=Fundamentals of Fingerprint Analysis|author=Hillary Moses Daluz|publisher=CRC Press|year=2014|isbn=978-1466597983|page=186}}</ref>

The collection of fingerprints off of a cadaver can be done in varying ways and depends on the condition of the skin. In the case of cadaver in the later stages of decomposition with dried skin, analysts will boil the skin to recondition/rehydrate it, allowing for moisture to flow back into the skin and resulting in detail friction ridges.<ref>{{Cite journal |last=Uhle |first=Aaron |date=2007 |title=The Boiling Technique: A Method for Obtaining Quality Postmortem Impressions from Deteriorating Friction Ridge Skin |url=https://www.proquest.com/openview/3d04d25e8751c0baed0d0ea0f10e66e2/1?cbl=29772&pq-origsite=gscholar&parentSessionId=qZqbYRdGwMX73nk4eM4%2BWZo3wm5poStY4vVZVNqWg7k%3D |journal=Journal of Forensic Identification |volume=57 |issue=3 |pages=358}}</ref> Another method that has been used in brushing a powder, such as baby powder over the tips of the fingers.<ref name=":7">{{Cite journal |last1=Morgan |first1=Lee O. |last2=Johnson |first2=Marty |last3=Cornelison |first3=Jered |last4=Isaac |first4=Carolyn |last5=deJong |first5=Joyce |last6=Prahlow |first6=Joseph A. |date=March 2019 |title=Two Novel Methods for Enhancing Postmortem Fingerprint Recovery from Mummified Remains |url=https://onlinelibrary.wiley.com/doi/10.1111/1556-4029.13876 |journal=Journal of Forensic Sciences |language=en |volume=64 |issue=2 |pages=602–606 |doi=10.1111/1556-4029.13876 |pmid=30025161 |s2cid=51702139 |issn=0022-1198}}</ref> The powder will embed itself into the furrows of the friction ridges, allowing the lifted ridges to be seen.<ref name=":7" />

=== Latent fingerprint detection ===
[[File:Dacty poederen.JPG|thumb|right|Use of fine powder and brush to reveal latent fingerprints]]
[[File:BurglaryIsrael2.jpg|thumb|right|Fingerprint dusting of a burglary scene]]
In the 1930s, criminal investigators in the [[United States]] first discovered the existence of latent fingerprints on the surfaces of fabrics, most notably on the insides of gloves discarded by perpetrators.<ref>{{cite news|title=O'Dougherty Urges All Be Fingerprinted: U.S. Attorney Describes Sciences of Crime Detection to Democrats|url=https://www.newspapers.com/image/52685974/|newspaper=The Brooklyn Daily Eagle|date=March 8, 1938|access-date=July 1, 2014|url-status=live|archive-url=https://web.archive.org/web/20140714155022/http://www.newspapers.com/image/52685974/|archive-date=July 14, 2014}}</ref>

Since the late nineteenth century, fingerprint identification methods have been used by police agencies around the world to identify suspected criminals as well as the victims of crime. The basis of the traditional fingerprinting technique is simple. The skin on the palmar surface of the hands and feet forms ridges, so-called papillary ridges, in patterns that are unique to each individual and which do not change over time. Even identical twins (who share their [[DNA]]) do not have identical fingerprints. The best way to render latent fingerprints visible, so that they can be photographed, can be complex and may depend, for example, on the type of surfaces on which they have been left. It is generally necessary to use a "developer", usually a powder or chemical reagent, to produce a high degree of visual contrast between the ridge patterns and the surface on which a fingerprint has been deposited.

Developing agents depend on the presence of organic materials or inorganic salts for their effectiveness, although the water deposited may also take a key role. Fingerprints are typically formed from the aqueous-based secretions of the eccrine glands of the fingers and palms with additional material from sebaceous glands primarily from the forehead. This latter contamination results from the common human behaviors of touching the face and hair. The resulting latent fingerprints consist usually of a substantial proportion of water with small traces of amino acids and chlorides mixed with a fatty, sebaceous component which contains a number of fatty acids and triglycerides. Detection of a small proportion of reactive organic substances such as urea and amino acids is far from easy.

Fingerprints at a crime scene may be detected by simple [[Fingerprint powder|powders]], or by chemicals applied ''[[in situ]]''. More complex techniques, usually involving chemicals, can be applied in specialist laboratories to appropriate articles removed from a crime scene. With advances in these more sophisticated techniques, some of the more advanced crime scene investigation services from around the world were, as of 2010, reporting that 50% or more of the fingerprints recovered from a crime scene had been identified as a result of laboratory-based techniques.

[[File:Fingerprint Identification Room.JPG|thumb|A city fingerprint identification room]]