Forensic Tools

These Forensic tools illustrate several principles in examining questioned text and images in biomedical science.

ORI's Forensic Image Analysis Tools may be available in two forms (depending in some cases on the specific task):

Forensic Droplets:
A "Droplet" is small desktop application in Adobe Photoshop®, (v.7 and later) that automatically processes image files that are dragged onto its icon. A Droplet can be a nearly "seamless" interface for quickly examining certain features of a scientific image in Photoshop while reading the publication in the FULL TEXT (html) form or in some forms in an Internet Browser. Droplets can be used to automate the batch processing by dragging and dropping a group of image files.

First, Download and Save the Droplet to the desktop and assign it's use to your Photoshop®, program. To use, simply select and drag the highest resolution image from the browser’s window to the desk top, where the image will be automatically saved. At this point, dragging the icon of the new desktop file onto the Droplet will 1) then open Photoshop (if it is not already open), and 2) trigger an automatic sequence for the specific Droplet selected.

Basic Forensic Actions

Advanced Forensic Actions

An "Action" is the sequence of steps that was pre-recorded in Photoshop®, but unlike the Droplet the Action is activated by command from within the Photoshop program. A Forensic Action sequence is more flexible than the Droplet; It can be customized by toggling certain features "on" or "off"; and it can be used to create a corresponding Droplets for automated batch processing. Because Actions tend to be "upwardly" compatible, they can be used to create Droplets that work with a new version of Photoshop.

Two Sets of Upgraded Forensic Imaging Tools are now Available:

ORI's upgraded Tools for image forensics have evolved considerably from their original form* that was introduced in February 2005. The upgraded tools are provided as two distinct sets.

  • Forensic Actions provide most of the basic features needed to analyze forensic images. Their functions are essentially identical to those of the original forensic tools which they replace, namely several procedures for the visualization of inconsistencies within an image and/or the comparison of two images by means of a color-coded overlay. (The latter process is no different that co-localization, a routine tool in cell microscopy.) These tools are straightforward and can be used for teaching, instruction, and also for forensic examinations. For several years they appear to have been employed satisfactorily by diverse users including institutions, scientists, journals, RCR trainers, students and an occasional reporter, and who had requested them. This set also includes a useful Look Up Tables for visualizations, and several "READ ME" files given specific recommendation for their use, further explanation, and for interpretation of the results.
  • Advanced Forensic Actions allow for analysts to save an analysis and then go back and try different conditions on each adjustment layer to provide an optimal result. These tools have extended features that will be more useful to institutional committees who are assessing image evidence in their inquiries and investigations. In particular, some of these Forensic Actions utilize "Adjustment Layers©" that allow reexamination of the result of a forensic test retrospectively. The original image is retained (and recoverable), since all changes are made only in the separate overlying layers that superimpose commands which can be modified or rearranged. The size of the image file is increased, but each additional layer preserves a detailed record the analytic step that is resident within forensic test. Results are easier to share.

    The added flexibility requires more stops for queries in an Advanced Forensic Action sequence, and so it is slightly less streamlined than the comparable Action sequence from the first set. Once the user gains familiarity with the sequence, however, the dialogue and decisions steps can be toggled "off" to speed the sequence for the initial result; at this point the settings for individual steps can be adjusted retrospectively as required. Analysis can be far more efficient, since the need to run multiple sequences to get a result is eliminated.

    The Advanced Forensic Action set also include additional convenient routines for "Setting up" a Forensic Work Space, the logging a record of the analysis as a automatically saved history text, and a "stop" for customizing Keyboard shortcuts. The advanced set also come with additional look-up tables for multiple forms of visualizations and contour overlays for comparing difficult images. Because these features add more decision points, the attached "Read Me" comments are important to understanding the consequence of using adjustment layers.

*ORI's original Forensic Droplets and Actions that are compatible with outdated versions of Photoshop (v7) have been archived, but they are still available upon request at AskORI@hhs.gov.

Considerations, Sample Images, and Forensic Test-Patterns:
This section discusses the methods, gives samples of images from past cases, and provides Forensic Image Test Patterns to evaluate the performance of the Droplet (or Action).

Source URL: https://ori.hhs.gov/forensic-tools