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Recommendations for Mobile Device Photography for Comparative Analysis

23-P-002-1.0

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Table of Contents

1. Purpose

The purpose of this document is to define the SWGDE position on the use of mobile device cameras to capture examination quality images of items where that image will be subjected to comparative analysis (e.g., latent prints). This document is specific to images captured by investigative organizations.

2. SWGDE Position

Although there have been advances in the quality of images captured by mobile device cameras, they are not all of the same quality. Mobile devices typically do not have the capability of traditional digital single lens reflex (DSLR) and mirrorless interchangeable lens cameras (MILC) used in advanced photography such as external removable flashes, interchangeable lenses, uncompressed or lossless file format options, etc. SWGDE recognizes there are instances where it may be necessary, in rare circumstances, to capture images on a mobile device camera and these images may still have limited acceptable uses. Examples of these circumstances include fleeting, or transient evidence or real-time investigative need due to an imminent public safety issue.

3. Considerations

3.1. Prior to purchasing or utilizing existing issued organization mobile devices inspect the specifications of the mobile device and consult the department photographers and comparative examiners for a quality assessment.

3.2. A personal mobile device should not be used.

3.3. Consult your organization guidelines for image transfer and storage.

4. Recommendations

If the only digital image capture method available is a mobile device, the following conditions should be met:

4.1. Any image captured should conform to all organization requirements and/or best practices [1], [2].

4.2. The camera should be set to the highest quality setting without any filters applied.

4.3. If the mobile device’s camera settings allow it, the highest aperture and lowest ISO should be utilized.

4.4. Place an approved scale with item identifier next to the evidence item and on the same plane as the detail to be captured.

4.5. Align the sensor plane parallel to the impression.

4.6. The item being photographed should be adequately lit. Specific lighting techniques should be used [3].

4.7. Ensure that subject matter details are in focus.

4.8. The mobile device’s native focal length should be used (i.e. 1x) and it is not recommended to use the zoom feature; whether it be the wheel feature or, “pinch to zoom”.

4.9. The image shall not be altered on the mobile device.

4.10. The image should be moved to agency storage as soon as possible and in the original format.

4.11. The image quality (e.g., resolution, size) should not be reduced when transferring it from the mobile device. Files transferred via email, text, or vendor application have a potential to degrade the image resolution and should be avoided, or tested to confirm there is no degradation prior to the transfer.

4.12. The image’s metadata should be preserved and not altered or deleted.

4.13. Notes should be made in the case record to reflect that the image was captured on a mobile device and the circumstances that required its use.

5. References

[1] Scientific Working Group on Digital Evidence, “Photographic Equipment and Infrastructure Recommendations”.
https://www.swgde.org/documents/published-by-committee/photography

[2] Scientific Working Group on Digital Evidence, “Digital Image Compression and File Formats Guidelines”.
https://www.swgde.org/documents/published-by-committee/photography

[3] Scientific Working Group on Digital Evidence, “Lighting Techniques for Forensic Photography”.
https://www.swgde.org/documents/published-by-committee/photography

6. History

Revision Issue Date History
1.0 DRAFT
1/9/2023
Reworked various sections and updated title of previous published document (SWGDE Mobile Device Photography for Comparative Analysis Position Paper), which will be replaced by this document.
1.0
6/13/2023
Additional work to all sections. Recommend to archive original position paper and publish mobile Device Photography for Comparative Analysis as new document.
1.0
8/7/2023
Formatted for posting after SWGDE membership voted to release as a Draft for Public Comment.
1.0
2/26/2024
Editorial changes made based on internal SWGDE member comments.
1.0
3/7/2024
Formatted for posting after SWGDE membership voted to release as a Final Publication.

Version: 1.0 (3/15/2024)

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