General Study Guide - Ontario Police College

4. Silver Physical Developer (Ag-PD) (1975)
Pre-wash with maleic acid (10 min. or until bubbles
disappear.)
Specimen is immersed up to 20 min. & item s/b
agitated (gentle rocking motion).
Post-wash in 3 separate distilled water baths for ~ 5
min. each before re-processing.
Grey
Chemical reaction with lipids, fats, oils
and waxes in print residue.
At present, no reagent has been as
successful as the Ag-PD for visualizing
the water-insoluable components of
latent print residue (fats and
oils/lipids, proteins) on paper.
Photograph.
* In their classes, the FBI is teaching a new method of using iodine. By mixing it with solvents and spraying it on papered or painted walls or paper
documents, latent prints are being developed which last several hours. Therefore, photography of latent prints developed using Liquid Iodine need not be
immediate. This method of spraying Liquid Iodine can be used at crime scenes if protective measures are taken. Iodine fumes are toxic & corrosive. Every
precaution should be taken to avoid inhaling iodine fumes. A full-face, self contained breathing apparatus and protective clothing such as coveralls and
gloves must be worn. CAUTION: The mixing and spraying of this solution must be done in a fume hood or while using a full-face breathing apparatus.
** Physical Developer (used immediately after item has been dryed and fluorescence examination) is especially successful in developing latent prints on
porous substrates that were previously wet. (Refer to Figure 5.8, pg.187, A.F.T. Flowchart for fingerprint visualization on paper and cardboard.) Sodium
hypochlorite can also be used post-PD on porous, previously wet items. PD also works well on clay fire bricks, concrete, latex or rubber gloves, both sides
of adhesive tape, rayon or nylon clothing, unfinished porcelain, unfinished wood and wooden knife handles.
***Thermal and Carbonless Papers are used for many current business applications and therefore “a fundamental understanding of its chemical and
physical properties is required to assist the examiner in deciding what possible method of chemical processing will not damage these specialty papers,
while subsequently allowing for the development of quality friction ridge detail on their surface.” (Jon T. Stimac, Journal of Forensic Identification, Vol.53,
Issue 2, 2003) Refer to separate article on Latent Print development on Thermal Paper in this study guide.