General Study Guide - Ontario Police College

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Titanium Dioxide (prints develop on non-adhesive and adhesive sides) White Chemical reaction – see separate article in this study guide for additional information. From OPC Notes for developing prints on “Balled Tape”… Tape may be separated for examination by heat, freezing or solvent. 1) Heat method – Use hair dryer at low or medium setting 2) Freezing method – Place tape in freezer until frozen solid or use a pressurized can of air sprayed directly onto the tape. 3) Solvent method – Use “Shandon Xylene” developed by the U.S. Army Criminal Investigation Laboratory. Under a ventilation hood/fuming cabinet & using gloves & eye protection, hold the tape with tweezers and use an eye dropper to apply very small amounts of the solvent to the tape at the line of adhesive. This method has also been effective in removing adhesive tape from paper or cardboard. Caution - Impression may be damaged from transfer of cells during separation of tape. Using the solvent method, fingerprints have been developed not only on the tape but also on the paper from which it was removed. The tape was examined using Crystal Violet and Ninhydrin was used on the paper. Developing Latent Prints on Tape – non-adhesive side. Proper development sequence and types of chemical processes – depending on the circumstances not all processes may apply. All processes, however, are post visual and examination of inherent fluorescence by laser and alternate light source. Latent Print Development Techniques and ‘Basics’ of Processing Procedure Development Colour Ridge Detail Visualized By Cyanoacrylate Fuming To protect adhesive side, place tape on a piece of clear acetate before CA. Vacuum Metal Deposition (see page ) White Fumes from the active cyanoacrylate ester polymerizes eccrine components of the print residue. Post-cyano dye stains &/or powders are used to further enhance the developed prints. Refer to separate table for a list of possible dye stains and appropriate forensic light sources. Powder Dependent on choice of colour. Contrast made between powder colour and substrate.
Development of Latent Prints on Thermal Paper - Manual of use for ThermaNin Introduction Thermal paper, once mainly used as fax paper only, is now used in many applications. These days it is used in ticket dispensers for giving out queue numbers or parking tickets, in label printers, and printers for point-of-sales receipts at retail shops like supermarkets. Thermal paper turns black on application of heat (as in the printer) but also on contact with polar solvents like alcohols, acetone, ether, ethyl acetate etc. The regular solutions of fingerprint reagents like ninhydrin and DFO are either based on a polar solvent (ninhydrin in ether or acetone for example) or rely on certain amounts of these polar solvents to dissolve them when used in an apolar bulk solvent like petroleum ether or heptane. These solutions have a detrimental effect on thermal paper: on application the paper surface turns dark grey or black thereby obscuring any fingerprints that may subsequently develop. There are only a few techniques known for developing fingerprints on thermal paper: 1,2-IND (as a 2 g/l solution in HFE-7100 containing 7% ethyl acetate) has been reported to develop fingerprints without darkening the top (active) layer of the thermal paper (John Stimac, Journal of Forensic Identification, 2003, 53(3), 265-271). For finding and photographing the developed prints a Polilight or similar light source is needed. DMAC (dimethylaminocinnamaldehyde) fumes react with fingerprints on thermal paper (see e.g. Brennan et al., Journal of Forensic Identification, 1995, 45(4), 373-380). The fluorescence of any developed prints can be photographed with green light (Polilight, around 530 nm). Exposure to the fumes of concentrated hydrochlorid acid was reported to develop prints on the top layer of thermal paper (Broniek, Knaap, Journal of Forensic Identification, 2002, 52(4), 427-432). It will not develop prints on the back of thermal paper. Treatment with a regular ninhydrin solution and after allowing ample time for development of fingerprints, rinsing the paper with an excess of acetone to remove all the text and/or grey-black stains.
Page 1 and 2: What to Study (Information from Ont
Page 3 and 4: evidence evidence for further exam
Page 5 and 6: h. Use alternate lighting sources a
Page 7 and 8: History of Fingerprint Identificati
Page 9 and 10: Harris Hawthorne Wilder, Ph.D. (191
Page 11 and 12: Friction Skin Structure Skin is one
Page 13 and 14: Friction Skin - Dermal Papillae The
Page 15 and 16: E- Evaluation: It is not sufficient
Page 17 and 18: 4. Silver Physical Developer (Ag-PD
Page 19 and 20: Metallic powders - consist of very
Page 21 and 22: Post-Cyanoacrylate Dye Stains Ardro
Page 23 and 24: 3. Modified Physical Developer (MMD
Page 25 and 26: Leucomalachite Green (RCMP) extrem
Page 27 and 28: Additional Latent Print Development
Page 29: Developing Latent Prints on Tape -
Page 33 and 34: Manual of use Due to the sensitivit
Page 35 and 36: Reagent Reacts With Type of substra
Page 37 and 38: SUBSTRATES AND SUGGESTED LATENT IMP
Page 39 and 40: Waxed cardboard (e.g. milk cartons,
Page 41 and 42: Examining the Crime Scene (O.P.C. T
Page 43 and 44: The only exception is paper exhibit
Page 45 and 46: Very approximate correlations betwe
Page 47 and 48: Procedures for conducting an examin
Page 49 and 50: For use on CA-treated prints, the l
Page 51: Alternate Light Source Reference Ch

General Study Guide - Ontario Police College

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