ESDA Examination
Definition
Electrostatic Detection Apparatus examination: reveals latent indentations from overlying writing, used in anonymous-letter cases to detect additional text written on sheets above the questioned document.
- Full name
- Electrostatic Detection Apparatus examination
- Reveals
- Latent indented writing from overlying sheets
- Use case
- Anonymous letter and threat letter cases
- Destructive to document
- No
Common questions
Why is ESDA particularly useful in anonymous letter investigations?+
An anonymous letter is often written on a pad, leaving faint indentations of other pages written above it that are invisible to the naked eye. ESDA can raise those indentations into a readable image, sometimes recovering drafts or other text the writer never intended to disclose.
Does ESDA examination damage or alter the original document?+
No, it is a non-destructive technique that develops the indentation image on a separate film without applying ink, heat or chemicals directly to the original page.
Related terms
- Behavioral Analysis (Threat Assessment)
- Assessment of anonymous threatening communication to classify threat type, estimate escalation risk, and generate investigative hypotheses, conducted by behavioral scientists, not a...
- Burrows' Delta
- A computational authorship attribution metric based on the frequency distribution of the most common function words in a text; widely used in...
- Disguised Writing
- Writing in which the writer has deliberately altered their habitual features to prevent identification; commonly involves changed slant, block capitals, opposite hand,...
- Exemplar Dictation Protocol
- The standard procedure for obtaining handwriting exemplars from a suspect without allowing them to see the questioned document first, to prevent stylistic...
- Forensic Linguistics
- The application of linguistic knowledge and methods to questions that arise in legal, law-enforcement, and judicial contexts, including authorship analysis, legal language...
- Linguistic Fingerprint
- The unique or highly individualising cluster of syntactic, lexical, and pragmatic habits that persists across a writer's texts and survives most physical...
- Natural Variation vs Disguise Variation
- Natural variation is the bounded spread of a genuine writer's habitual features; disguise variation is larger and shows an effort signal (heavier...
- Proportion Ratio
- The height-to-width or stem-to-body relationship within individual letters; encoded in long-term spatial memory and largely preserved under disguise, opposite-hand writing, and block-capital...
- Slant Drift
- The progressive reversion of disguised writing slant toward the writer's habitual slant as the document lengthens and cognitive load increases.