Fingerprint Identification Flashcards
Explain the method you use to identify a fingerprint?
We first analyse the shape and pattern of the latent fingerprint, as well as the amount and clarity of detail contained within it.
If suitable, we then compare the latent fingerprint to a fingerprint from a known person.
A fingerprint identification is established when two fingerprints are shown to contain the exact same unique arrangements of ridge characteristics.
All fingerprint identifications must be verified by two other fingerprint officers, who must carry out their own independent comparison of the two fingerprints, and must agree with identification before it can be disclosed.
What makes a fingerprint ‘suitable for comparison’?
When analysing a fingerprint, we are analysing the clarity of detail available for comparison; i.e. how clearly the unique features of the skin have been replicated in the fingerprint.
The clarity of a fingerprint is affected by various factors, including the type of surface being touched (i.e. the material and texture of the surface), as well as the amount of pressure applied to the surface.
The clarity of a fingerprint will determine how much detail is available for comparison - the fingerprint will only be compared if it contains sufficient quality and quantity of ridge detail.
When comparing two fingerprints, what are the features that you are comparing?
When comparing two fingerprints, we compare the shape and relative position of the features in each fingerprint.
These features include any deviations in the shapes of the ridges; such as areas where one ridge splits into two, where ridges stop and start; as well as any scars and creases.
What are the different conclusions of a fingerprint comparison?
Following a fingerprint comparison, one of three conclusions, or evaluations, may be made:
If two fingerprints display the same unique arrangement of ridge features, we will conclude the two fingerprints were formed by the same person - this is known as a fingerprint identification.
If the fingerprints do not display corresponding ridge features, we will conclude the two fingerprints were not formed by the same person.
Finally, if there is insufficient quality and quantity of ridge detail in either of the fingerprints being compared, we will conclude that there is insufficient detail for a conclusion to be made.
How many features are required to identify a fingerprint?
There is no set number of features required to identify a fingerprint - this is because the clarity of ridge detail, as well as the type of features available in every fingerprint is different.
Features such as scars and short ridges, are more unusual, or unique than others, and therefore contribute more to an identification; and,
The clarity of a fingerprint determines the quality of detail available for comparison.
What do you mean by ‘clarity of detail’?
When analysing a latent fingerprint, we are analysing the clarity of detail available for comparison; i.e. how clearly the unique features of the skin have been replicated in the fingerprint.
The clarity of a fingerprint is affected by various factors, including the type of surface being touched (i.e. the material and texture of the surface), as well as the amount of pressure applied to the surface.
The clarity of a fingerprint will determine how much ridge detail is available for comparison - the latent fingerprint will only be compared if it contains sufficient quality and quantity of ridge detail.
How did you identify the defendant?
Fingerprint labelled ‘AA06’ was searched on the NZ Police Fingerprint database using computer software called ABIS, which stands for the Automated Biometric Identification System.
Following this search, ABIS produced a list of candidates with similar features to those contained within fingerprint AA06, of which the left thumb of Graham HARRISON was the first candidate.
I then carried out a comparison of all the features contained within fingerprint AA06 with those contained within the left thumb of Graham HARRISON and concluded that these two fingerprints originate from the same person.
I then compared all remaining fingerprints that I preserved from the scene, and from exhibits from the scene, to the fingerprints recorded on the NZ Police fingerprint forms bearing the name Graham HARRISON.
What is ABIS?
We use special computer software, called ABIS, for searching latents against fingerprints on the Police fingerprint database. This software creates digital maps from latent fingerprints, which it uses to search against fingerprint maps held in the Police database.
Rather than being able to find identical matches, this software creates a list of fingerprints which share similar maps to that of the latent fingerprint - we then compare the latent to each of the fingerprints in the list to see if any of them match.
How sure are you that you have identified my client?
I am absolutely certain that I have correctly evaluated all fingerprints identified to Graham HARRISON.
Why does it mean that this fingerprint has been enhanced?
Before analysing and comparing a fingerprint, I turn the fingerprint image to black and white. This helps to enhance the contrast between the fingerprint and its background, and makes it easier to examine the finer details of the fingerprint.
Contrast may be further enhanced using specific computer software, which acts to enhance the contrast between the fingerprint and the background without materially altering the image.
Is the process you use to identify fingerprints always the same?
Based on the complexity of a latent fingerprint, the amount of time I spend analysing and comparing the latent fingerprint will differ, however, I always apply the same methodology, which is the ACE-V methodology, whenever I am identifying a fingerprint.
When you conduct comparisons of fingerprints do you take notes?
I record working notes when analysing a latent fingerprint to show the location and sequence of unique features contained within it, and also when comparing the latent fingerprint to a known fingerprint to show areas of correspondence between the two fingerprints.
Outline your reasoning for your opinion about the fingerprint identifications.
All fingerprints identified to Graham HARRISON were established based on corresponding ridge features, with the same shape location and sequence.
How did my clients fingerprints end up on the fingerprint database?
I am happy to answer this question; however, with all due respect, I believe that this question would be best answered without the jury present.
Whenever someone is arrested, their fingerpints and other biometric data is recorded, and if charged for that offence this data will remain on police databases.
When searching latent fingerprints on the NZ Police fingerprint database, we are searching this latent fingerprint against all fingerprints that have recorded from those people that have been previously arrested for an offence.
Why does the latent fingerprint look different to the known fingerprint?
Even fingerprints from the same finger look slightly different, and this is because of the range of factors that influence how clearly the unique features of the friction ridge skin are reproduced in fingerprints.
These factors relate to the person leaving the fingerprint, such as the condition of their skin, the amount of sweat (and other residue) on their skin, and the amount of pressure they apply to the surface; as well as factors relating to the surface being touched, such as how clean or textured the surface is.
Whenever a latent fingerprint is left on a surface, the appearance of that fingerprint is affected by a unique combination of these factors.
Fingerprints on record, on the other hand, are recorded under highly controlled conditions to maximise the amount of detail recorded from the friction ridge skin. Therefore, we often see slight differences in the appearance of latent and known fingerprints due to the differences in how they have been produced.
