Fingermark identification
Fingermark identification
This video will cover how fingermarks recovered from crime scenes are compared to fingerprints using automated systems and by fingerprint examiners, and how the ridge details present in the fingermarks can be used for identification. How does a visible fingermark or latent fingermark that has been enhanced from a crime scene lead to the identification of an individual? When a fingermark is recovered, it is generally photographed. This image is uploaded to a database which holds fingerprints from known individuals as well as fingermarks from other crime scenes which have not been identified. In the UK, this database is called IDENT1. However, in the US and other countries, it is referred to as AFIS, which is the automated fingerprint identification system.
If the database produces a match, this is further verified by trained fingerprint examiners. This is a subjective comparison. However, the comparison is always conducted by at least one other examiner. If the examiners are in agreement, then it is reported as a definitive match or non-match. We’ve shown in the fingermark enhancement video how fingermarks are recovered at crime scenes. But how are fingerprints taken from known individuals? Every person arrested in England, Scotland, and Wales for a recordable offence has their fingerprints, palm prints, and limited nominodata taken and entered onto the Ident1 database. There will be similar legislation in other countries about the taking of fingerprints on an individual’s arrest. You may also be asked to provide a set of elimination fingerprints.
For example, if your home has been broken into and the police want to exclude your fingermarks from any fingermarks the burglar may have left behind during the offence. Traditionally, fingerprints were taken using ink and Tenprint cards. Tenprints are taken by rolling the fingertips in ink and leaving a rolled impression, which is a recording of all the ridges from one side of your fingernail to the other on a pro forma such as the one shown. The rolled fingerprints are the square-shaped fingerprints in the middle of the pro forma. It also records fingerprints which have not been rolled, just placed down onto the pro forma, like this, at the bottom of the pro forma shown.
Palm prints are also taken and are recorded on the back. The Tenprint would then be scanned and the fingerprints uploaded to the database. Livescan is the capture of fingerprint and palm images without ink using an electro-optical computerised device. Images can be transferred directly to the database using this method. If a match is found between a fingermark from a crime scene and a fingerprint in the database, fingerprint examiners will compare the two marks using the ACE-V methodology.
The first step requires the fingerprint examiner to examine and analyse all variables influencing the fingermark in question. Some of these factors include the deposition surface, the enhancement process, pressure, and distortion, to name a few. The quantity and quality of the latent print ridges influences the examiner’s ability to perform the next phase. C is for comparison . The comparison process introduces the fingerprint with which the fingermark is to be compared. The comparison process compares the various features present within the overall patterns. E is for evaluation. Three conclusions can be made. Firstly, the fingermark and fingerprint were made by the same finger of the same person.
Secondly, the fingermark was not made by the person whose fingerprint was identified by the database, or thirdly, the results were inconclusive generally due to the lack of adequate clarity or the absence of comparable area and the known exemplar. V is for verification, the final part of the process. The general rule is that all identifications must be verified by a second qualified expert. As mentioned previously, there are three different levels of detail in which a fingermark can be compared to a fingerprint. 1st Level Detail examines the overall pattern in the fingerprint. Individuals generally have a mixture of pattern types in their fingertips with some correlation between the left and right hands.
There is also evidence that the general fingerprint pattern may be genetically determined. While the loop pattern is the most common pattern, classification of individuals by assigning a pattern type to each of the 10 fingers in an ordered fashion serves as the first line of discrimination.
2nd Level Detail examines the ridge characteristics. These characteristics, such as a ridge ending or when a ridge splits into two ridges, are called minutiae. The locations of these minutiae in a fingermark are compared with minutiae points in the fingerprint. A single rolled fingerprint may have as many as 100 or more minutiae that can be used for identification purposes. The number of minutiae found in a fingermark depends on the area of the finger that the mark was deposited from. For example, the area containing the fingerprint pattern will contain more minutiae per square millimetre than the area near the tip of the finger. 3rd Level Detail looks at the pores and edges of the ridges.
Sweat pores within the ridges are variable in size, shape, position, and frequency along the ridge and can have variable frequency along the ridge. This concept, coupled with that of edgeoscopy, which refers to the individuality of the ridge edges, is what makes up the 3rd Level Detail for identification. The following images show 1st Level Detail fingerprint patterns. These images show arch-type patterns. A regular arch can be seen in the middle of the image, but compare this to the tented arch, which is more sharply pointed at the top of the arch, will distinguish between the two. Loops are the most common fingerprint pattern.
Loops can come in from the right-hand side of the fingerprint, as in the left-hand image, or they can also come from the left. A double loop is also possible where the ridges loop down and around before looping up and around. It can also be reversed like a regular loop. Whorl patterns are a circular-like pattern, and it is also possible to get a mixed pattern.
The following images show examples of 2nd Level Detail. The table shows the possible minutiae that can be found in a fingermark or fingerprint, and it is the minutiae and their relative position that can be used for comparison. The image shows a fingerprint with various labelled minutiae.
The following image shows 3rd Level Detail. It is examined at a higher magnification than the other levels. The formation of the pores and the ridges would be compared on a fingermark to a fingerprint.
In the UK, a fingerprint identification was originally verified if two fingerprint examiners could find 16 minutiae which were matched between a fingermark and a fingerprint. However, the UK now undertakes comparisons in accordance with the non-numeric fingerprint standard. This means that fingerprint examiners no longer need to match a minimum of 16 minutiae to make an identification. The inclusion of 3rd Level Detail and the experience and judgement of the fingerprint examiner is now used in addition to the comparison of 1st and 2nd Level Detail. By watching this video, you should now be able to describe how fingermarks are compared to fingerprints, describe the ACE-V method, describe the three levels of ridge detail in fingerprints.
This video deals with the characteristics within a fingerprint and fingermark that are used in the identification process.
But first we have to look at how such comparisons would be undertaken. Fingerprint examiners follow a defined process known as ACE-V which you read about in the Nature article earlier this week. ACE-V facilitates a systematic approach to the examination and comparison process. Exemplar fingerprints must also be taken so that a comparison with an enhanced or lifted mark can be made.
There are a number of different levels of detail that may be present in the recovered mark and these are explained and discussed. Later in the week, you will be presented with a simple method to let you take your own fingerprints. If you decide to do so, come back and re-look at this video so that you can use the information to identify the features in your own fingerprints.
Reach your personal and professional goals
Unlock access to hundreds of expert online courses and degrees from top universities and educators to gain accredited qualifications and professional CV-building certificates.
Join over 18 million learners to launch, switch or build upon your career, all at your own pace, across a wide range of topic areas.
