Fingerprint Identification

Question 1

What method do you use to identify fingerprints?

Answer 1

We use a method called ACE-V, which is an acronym that represents that sequence of steps that must be carried out whenever we identify a fingerprint.

The first step involves a thorough analysis of all available information in the latent fingerprint. This includes the shape and general pattern of ridges, as well as the amount and clarity of ridge detail contained within the fingerprint.

The latent fingerprint is then directly compared to fingerprints from a known person. This step involves systematically comparing the shape, location and sequence of all ridge features contained within the latent fingerprint with those contained within the known fingerprint.

If the two fingerprints share sufficient corresponding ridge features with the same shape, location, and sequence, it may be concluded that the two fingerprints were formed by the same person. This is also known as a fingerprint identification.

Alternatively, if the two fingerprints do not share corresponding ridge features with the same shape, location, and sequence, it may be concluded that the two fingerprints were not formed by the same person.

If it has been concluded that the two fingerprints were formed by the same person, two other qualified fingerprint officers must carry out their own independent analysis and comparison of the two fingerprints and must arrive at the same conclusion as the initial examiner before an identification is established.

Question 2

Do you make errors?

Answer 2

I am susceptible to making errors, just like any other person; however, I am confident that I have made no errors in relation to the fingerprint identifications before me as I strictly adhered to the standard operating procedures prescribed in my office and to the ACE-V methodology.

I also carried out a thorough review of all of my documentation prior to submitting these fingerprint identifications for verification, and carried out a second review of all of my documentation while preparing my file for court purposes.

Question 3

How do you prevent bias from influencing fingerprint identifications?

Answer 3

As part of the fingerprint officer training programme we receive training to identify and mitigate potential sources of bias. This includes:

Carrying out a thorough analysis of the latent fingerprint before comparing it to a known fingerprint. This ensures that we are not biased by the information contained within the known fingerprint.

Limiting unnecessary exposure to case information prior to analysing and comparing a latent fingerprint to a known fingerprint. This ensures that we are not biased by extraneous information that is not directly relevant to the fingerprint identification process.

These factors ensure that the fingerprint identification process is guided predominantly by the information present in the latent fingerprint, therefore limiting the effects of bias.

Because I followed these procedures, I am confident that bias did not affect my judgements in relation to the fingerprint identifications before me.

Question 4

How did you identify the defendant?

Answer 4

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.

Question 5

What is ABIS?

Answer 5

ABIS, or the Automated Biometric Identification System, is computer software that we use for searching latent fingerprints against fingerprints held on the NZ Police fingerprint database.

We search fingerprints by marking the location and sequence of unique features, which ABIS uses to search the fingerprint against the fingerprints held on the database.

Following the search, ABIS produces a list of fingerprint candidates with similar features. We then go through each candidate and compare the location and sequence of all ridge features contained within the latent and known fingerprints to determine whether any of them originate from the same person.

As with any other fingerprint identification, identifications established through ABIS must be verified by two other qualified fingerprint officers before it can be disclosed.

Question 6

How sure are you that you have identified my client?

Answer 6

I am absolutely certain that I have correctly evaluated all fingerprints identified to Graham HARRISON.

Question 7

Why does it mean that this fingerprint has been enhanced?

Answer 7

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.

Question 8

Is the process you use to identify fingerprints always the same?

Answer 8

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.

Question 9

When you conduct comparisons of fingerprints do you take notes?

Answer 9

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.

Question 10

Outline your reasoning for your opinion about the fingerprint identifications.

Answer 10

All fingerprints identified to Graham HARRISON were established based on corresponding ridge features, with the same shape location and sequence.

Question 11

What process is carried out when examiners disagree over a fingerprint identification?

Answer 11

We have standard operating procedures for situations where examiners disagree over the conclusions of a fingerprint identification; however, in this case, there were no disagreements in terms of my own conclusions and those made by the verifying examiners.

Question 12

Is fingerprint identification infallible?

Answer 12

No scientific method is infallible; however, with strict adherence to ACE-V and standard operating procedures, any errors during the fingerprint identification process may be prevented.

Question 13

Isn’t fingerprint identification just one person’s subjective opinion?

Answer 13

Fingerprint identifications are established based on the subjective opinion of not only the initial examiner, but also two other qualified fingerprint officers. And although subjective, it is an opinion that is formed based on the extensive training, knowledge, and experience of those three examiners.

Question 14

Are you aware of a known error rate for fingerprint identification?

Answer 14

There is currently no consensus in the fingerprint science community as to a known error rate for fingerprint identification.

Question 15

Are you familiar with the NAS/PCAST reports?

Answer 15

I am aware that this report was carried out to investigate the reliability of the various forensic science disciplines.

From these reports, a number of recommendations were made to ensure the reliability of these sciences, which helped to shape the standard operating procedures that we use today.

Question 16

How did my clients fingerprints end up on the fingerprint database?

Answer 16

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.

Question 17

Are you aware of the McKie and Mayfield errors?

Answer 17

I am aware that bias played a significant role in causing these errors.

As part of the fingerprint officer training programme we receive training to identify and mitigate potential sources of bias. This includes:

Carrying out a thorough analysis of the latent fingerprint before comparing it to a known fingerprint.

Limiting unnecessary exposure to case information prior to analysing and comparing a latent fingerprint to a known fingerprint.

These factors ensure that the fingerprint identification process is guided predominantly by the information present in the latent fingerprint, therefore limiting the effects of bias.

Because I followed these procedures, I am confident that bias did not affect my judgements in relation to the fingerprint identifications before me.

Question 18

What does it mean for a fingerprint to be ‘unsuitable for comparison’?

Answer 18

When analysing a latent fingerprint, we assess the amount of ridge detail contained within the fingerprint, as well as the clarity of that detail. If the latent fingerprint contains an insufficient amount of clear and unique ridge detail, it is deemed unsuitable for comparison.

The amount of ridge detail required for comparison depends on the clarity of the fingerprint - for example, with fingerprints that contain clear ridge detail we can examine the finer features of the fingerprint, for example the shapes of the individual ridges. As these finer features of the fingerprint are highly unique, the amount of detail required to establish an identification is less than what would be required in a fingerprint that lacks clarity and does not contain these finer features.

Question 19

How much detail is required to establish an identification?

Answer 19

There is no set number of corresponding features required to establish an identification, but rather, the amount of detail required depends on the clarity of the fingerprint.

For example, with fingerprints that contain clear ridge detail we can examine the finer features of the fingerprint, such as the shapes of the individual ridges.

As these finer features of the fingerprint are highly unique, the amount of detail required to establish an identification is less than what would be required in a fingerprint that lacks clarity and does not contain these finer features.

Question 20

Why does the latent fingerprint look different to the known fingerprint?

Answer 20

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.

Question 21

What do you mean by clarity?

Answer 21

The clarity of a fingerprint refers to how clearly the unique features of the friction ridge skin are reproduced in a fingerprint.

Clarity can be affected by factors relating 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.

For example, a fingerprint left on a smooth, clean surface, such as a glass cup will likely have greater clarity than a fingerprint left on a dirty or textured surface, such as an old windowsill.