ROLE OF NEUTRON ACTIVATION ANALYSIS IN POLICE SCIENCE (FROM POLICE IN AUSTRALIA - DEVELOPMENT, FUNCTIONS AND PROCEDURES, 1977, BY KERRY L MILTE AND THOMAS A WEBER SEE NCJ-50485)

• NCJ Number: 50499
• Author(s): J GOULDING
• Date Published: 1977
• Length: 10 pages
• Corporate Author: Butterworth Pty Ltd
• Publication Format: Document
• Language: English
• Country: Australia

Annotation

THE PROCESS OF NEUTRON ACTIVATION ANALYSIS IS EXPLAINED, AND APPLICATIONS OF THAT PROCESS IN FORENSIC SCIENCE, PARTICULARLY IN AUSTRALIA, ARE DESCRIBED.

Abstract

NEUTRON ACTIVATION ANALYSIS IS A PARTICULARLY VERSATILE MEMBER OF A FAMILY OF TECHNIQUES FOR EVALUATING TRACE PARTICLES. THE TECHNIQUE INVOLVES MAKING A SAMPLE RADIOACTIVE BY BOMBARDING IT WITH NEUTRONS. THE DECAY PROPERTIES OF THE RADIATION FROM THE ACTIVATED SAMPLE ARE MEASURED, AND RADIONUCLIDES (RADIOACTIVE NUCLEI) ARE ISOLATED AND IDENTIFIED BY MEANS OF THEIR 'NUCLEAR FINGERPRINTS.' (THE RADIONUCLIDES OF EACH SUBSTANCE PRODUCE A CHARACTERISTIC SPECTRUM.) WHEN DECAY PROPERTIES CANNOT BE MEASURED DIRECTLY, RADIONUCLIDES CAN BE SEPARATED CHEMICALLY AND IDENTIFIED INDIVIDUALLY. BY ONE METHOD OR THE OTHER, ALL ACTIVATED NUCLEI IN A SAMPLE CAN BE MEASURED OR IDENTIFIED. NEUTRON ACTIVATION ANALYSIS IS VALUABLE IN FORENSIC SCIENCE BECAUSE IT IS EXTREMELY SENSITIVE FOR A LARGE NUMBER OF ELEMENTS, BECAUSE IT CAN BE APPLIED TO VERY SMALL SAMPLES, AND BECAUSE IT CAN DETECT SEVERAL ELEMENTS SIMULTANEOUSLY. IN ADDITION, THE PROCESS IS INDEPENDENT OF CHEMICAL ASSOCIATIONS OF THE ELEMENT BEING SOUGHT. IN SOME CASES (INORGANIC SAMPLES, ORGANIC SAMPLES EXPOSED TO SHORT IRRADIATIONS), THE SAMPLE NEED NOT BE DESTROYED. SINGLE-ELEMENT ANALYSES HAVE BEEN PERFORMED ON GUNSHOT RESIDUE (E.G., DETERMINATIONS OF WHETHER A SUSPECT HAS FIRED A SPECIFIC WEAPON) AND ON TOXIC METALS IN BIOLOGICAL MATERIALS (E.G., ARSENIC ON HAIR). MULTIELEMENT COMPARISONS (HEROIN, PAINT, GLASS, ETC.) HAVE GENERATED BOTH PRAISE AND CONTROVERSY. THE CONTROVERSY HAS CENTERED ON THE APPROPRIATENESS OF NEUTRON ACTIVATION ANALYSIS FOR 'DYNAMIC' SAMPLES, SUCH AS HAIR. NEUTRON ACTIVATION ANALYSIS IS A VALUABLE TECHNIQUE, BUT IT IS NOT A PANACEA. FORENSIC SCIENCE HAS ABOUT 20 INSTRUMENTAL METHODS OF CHEMICAL ANALYSIS, EACH WITH ITS OWN CHARACTERISTIC ADVANTAGES AND DISADVANTAGES. TABLES AND CHARTS DOCUMENTING THE RESULTS OF SEVERAL NEUTRON ACTIVATION ANALYSES PERFORMED IN POLICE INVESTIGATIONS ARE INCLUDED. (LKM)