Tonal Transitions: Causes and Visual Effects (11/06/2024)


Webinar Date

Nov 06, 2024

Webinar Time

9am-1pm PST

Webinar Duration

4 hours

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Instructor: Alice White

This webinar is adapted from elements of the Analysis of Distortion in Latent Prints workshop that Alice has taught since 2006. Ideally, the ridges in the friction ridge skin contact a surface and transfer an even coating of residue to the surface. This residue is then targeted by a latent print development technique, resulting in an impression that has distinctive ridges and furrows that require minimal eye strain to follow. But the world of latent prints is rarely so neat and tidy.

In this webinar we will look at many ways the ridges and furrows stray from this ideal condition. We will first discuss the composition of latent print residue (it is NOT 98-99% water as many of us were told). We will then discuss the different ways residue can be distributed across the surface of the skin and how this distribution matters when a surface is touched. After contact with a surface has been made, the manner in which the skin slides through the residue wreaks all kinds of havoc on the tone of the ridges and furrows – we will explore the many visual anomalies associated with movement. Lastly, we will discuss the impact of surfaces that already have contaminants and how this affects the transfer of residue, and consequently the appearance of the ridges and furrows.

Learning Outcomes:

  1. The attendee will be able to describe the three-dimensional features of the friction ridge skin.
  2. The attendee will be able to list the main components of latent print residue.
  3. The attendee will be able to describe the different ways residue can be distributed on the friction ridge skin.
  4. The attendee will be able to describe how the distribution of the residue on the skin impacts the transfer of the residue to a surface and creates tonal transitions.
  5. The attendee will be able to recognize variation in ridge and furrow appearance due to movement of the friction ridge skin on a surface.
  6. The attendee will be able to explain how contaminated surfaces can impact the tonal appearance of ridges and furrows.

Course Handout

Prior to the webinar (typically 1 – 2 days) you will receive an email link to a file or folder to download the handout and any relevant supplemental information. The main course handout can also be downloaded from the webinar platform at the time of the webinar.

Assessing Learning Outcomes (a.k.a. Quiz): In order to verify the learning outcomes have been achieved, there is a 20-question quiz via SurveyMonkey at the end of each webinar. Attendees must score a minimum of 70% on the quiz in order to receive a training certificate for the webinar. Please note the quizzes are open-book and poll questions are given during the webinar to prepare attendees for the quiz.

Attendance Policy

This webinar may only be attended by the person who is registered for the webinar. Evolve Forensics does not permit broadcasting, watching, listening, or distributing the webinar or any of the webinar handouts to individuals who are not registered for this webinar.

Software Requirements: Attendees must be able to access GoToWebinar (webinar platform) and SurveyMonkey (quiz platform) in order to participate.

The following YouTube Video shows how to use GoToWebinar as an attendee:


Please contact Alice White via email at

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