NCJ Number
62080
Date Published
1978
Length
16 pages
Annotation
THIS REPORT DETAILS THE DESIGN AND EVALUATION OF A LIGHT-TIGHT SACHET WHICH PERMITS AUTORADIOGRAPHY USED IN DETECTING FINGERPRINTS TO BE CONDUCTED IN DAYLIGHT.
Abstract
THE SACHET IS NEEDED IN ORDER TO HANDLE LARGE OR IRREGULARLY SHAPED ARTICLES FOR WHICH THE USUAL AUTORADIOGRAPHY TECHNIQUES ARE UNSUITABLE. TWO MATERIALS EXAMINED FOR THEIR SUITABILITY WERE BLACK POLYTHENE OF 40 MICRONS THICKNESS AND MELINEX FILM OF SIX MICRONS THICKNESS, COATED ON BOTH SIDES WITH ALUMINUM AND A PROTECTIVE LACQUER. THE MATERIALS WERE TESTED FOR THEIR ABILITY TO BLOCK LIGHT WHILE TRANSMITTING BETA RADIATION FROM THE ISOTOPE (SULPHUR 35) USED IN THE FINGERPRINT DETECTION. SINGLE LAYERS OF BOTH MATERIALS ALLOW LIGHT THROUGH, BUT DOUBLE LAYERS BLOCKED LIGHT. THE POLYTHENE, HOWEVER, ABSORBED MORE THAN TWICE AS MANY BETA PARTICLES AS THE MELINEX, SIGNIFICANTLY INCREASING THE NECESSARY AUTORADIOGRAPHY TIME. THEREFORE, A DOUBLE LAYER OF MELINEX WAS FOUND TO BE MOST SUITABLE FOR THE PROCESS. FOR RADIOGRAPHY TO BE CONDUCTED IN DAYLIGHT USING TWO LAYERS OF MELINEX FILM AND AN OPAQUE BACKING, ENOUGH PRESSURE MUST BE APPLIED TO MAINTAIN INTIMATE CONTACT BETWEEN THE SACHET AND THE SAMPLE UNDER EXAMINATION, AND THE NORMAL AUTORADIOGRAPHIC EXPOSURE TIME SHOULD BE INCREASED BY A FACTOR OF 1.50. OPERATIONAL COMPARISONS OF THIS TECHNIQUE WITH REGULAR TECHNIQUES ARE RECOMMENDED. SAMPLES OF THE MATERIALS TESTED, A REFERENCE LIST, A FIGURE, AND ILLUSTRATIONS ARE INCLUDED WITH APPENDIXES SHOWING RESULTS USING TWO ACTUAL CASES AND DIAGRAMS OF THE SACHETS' DESIGN AND CONSTRUCTION. (CFW)