If you have issues viewing or accessing this file, please contact us at NCJRS.gov. LABORATORY PROFICIENCY TESTING PROGRAM ,1I \... TI-IE FORENSIC SCIENCES FOUNDATION, ING. ) LABORATORY (PROFICIENCY TESTING PROGRAM REPORT NO.4 GLASS EXAMINATION PROJECT ADVISORY COMMITTEE )J. F. Anderson J.D. Chastain Ri chard H. Fox 'Spokane, Washington Aus ti n, Teltas Independence, Missouri Q '\ Anthony Longhetti Charles McInerney Andrew H. Principe San Bernardino, Ca. Pittsburgh, pa. Highland Park, Illinois John Thornton B. Edward Whittaker Be rke 1ey, Ca. Mi ami, Flori da PROJECT STAFF K. S. Field E. Fabri cant c ,,'. Prepared for the Departmgn1: of JIl~~lce, Law Enforcement Assistance A~minlstratlon, Nationa'I' lnsti tute of law EnforCEment and Criminal Justice, 'under Grant 74-NI-99-004B. Polnts o[view or oolnions stated in this document are those of the G·' authors and do not' necessarily represent the official positl~n or polfdes of the ,U.S. Department of Justice. ') : ,~ ,;. 0"_==-'-'"_--;=---="=-= () o - .--------------------------~~-~- FOREWORD The gnalysis summarized in this report is the fourth of a series that will be made in conjunction with this proficiency testing research project. In the course of this testing program participating laboratories will have analyzed and identified ten different samples of physical evic\ence similar in nature to the types of evidence normally submitted to them for an'alysis: The results of Test Number Four are reflected in the charts and graphs which follow. The citing of any product or method in this report is done solely for reporting purposes and does not constitute an endorsement by ,the project sponsors. Comments or suggestions relating to any portion of this report or of the program in general will be appreciated. July 1975 = (j TABlE~FCONTENTS Page FOREWARD . ii BACKGROUND . .. 1. SUMMARY. .. 2. ANNEX A - DATA SHEET . 3. :\) FIGURE 1. DATA SHEET USED FOR TEST NO.3 ANNEX B - NATIONAL BUREAU OF STANDARDS ANALYSIS 4. TABLE 1. CODE NUMBERS OF RESPONDING LABORATORIES 5 TABLE 2. SUPPLIERS CHARACTERIZATION OF SAMPLES .. 6 TABLE 3 . RESULTS FROM THREE REFEREE LABORATORIES 7 t d Ii TABLE 4. RESPONSES TO QUESTION 1 ....... 9 TABLE 5. REFRACTIVE INDEX AND DENSITY DIFFERENCES. 10 TABLE 6. RELATIVE FREQUENCIES OF THE REPORTED METHODS 11 TABLE 7. RESPONSES TO QUESTION 2 . ~ .. 12 TABLE 8. RESPONSES TO QUESTION 3 21 TABLE 9. METHODS ..•..... 30 (: I) BACKGROUND This laboratory proficiency testing research project, one phase of which is summarized in this report, was. initiated in the fall of 1974. This is a research study of how to prepare and distribute specific samples; how to analyze laboratory results; and how to report those results in a meaningful manner. The research will bec:onducted in two cycles, each of .' which will include five samples: a controlled substande; firearms evid~nce; blood; glass, and paint. Participation in the program is voluntary. AccordYhgly, invitations have been extended to 235 laboratories to share in the research. It is recognized that all laboratories do not perform analyses of all possible types of physical evidence. Thus, in the data summaries included in this report, space opposite some Code Numbers (representing specific laboratories) may be blank, or marked "No Data Returned." G A final project report will be prepared at the conclusion of Cycle II. The Project is under the direct control of the Project Advisory Committee whose.members' names are listed on the Title Page. Each is a nationally known criminalistic laboratory authority. " Supporting the Project Advisory Committee in their efforts is the Forensic Sciences Foundation with additional support from the National Bureau of Standards in the areas of sample evaluation and data analysis and interpretation. o 1. ~ -,,-~ . I .SUMMARY Te$t Sample #4 cons.isted of glass samples A and B, packaged in a plastic box. The samples were mailed on April 28, 1975 with instructions to handle the sample in a manner similar to like evidence and submitted for analysis. T~st Sample #4 was sent to 2~4 laboratories. Three of those laboratories served as referees, reducing the actual number to 231. In the accompanying data summaries, 124 laboratories responded with completed data sheets, '49 laboratories responded that they did not do glass analysis and no response was received from 61 laboratories. This represents a participation rate of 68%. No effort was made in this report to highlight areas wherin laboratory improvements might be instigated. \~ , 2. { ''; ANNEX A FIGURE'l., LAB CODE /1- ______ oCHECK HERE (AND RETURN) IF YOU 00 IIOT PERFORM GLASS EXAMINATION DATE RECEIVED IN LAB MTE P"OCESSEII IN lAS,____ _ OIlTA~ PROFICIENCY TESTING PROGRAM TEST 14 GLASS EXAMINATION Hem A represents a glass sample taken frO!ll the scene of a burglary. Item B represents a glass sample taken frORl the trousers of " 'suspect. 1. Item II could have cOl!11lOn origin with Item B. o 0 YES 0 110 0 Inconclusive 2. What Infonnatfon (quantitative and qualitative) did yoo develop to arrive at your conclusion in No. 11 lli!!.l. ,.- 2 • 3. Method(S) and Instl"UlMnt(sl used: ij DAT.~ SHEETS. H!lST 8E SECEIVED AT THe fOU/IDATION OFFlCE:BY .~IAY 3D! 1975 • ...._-------- ....--~-l"!f ... i,i-I -:i' ((... ', __ ...... -------- .....-- ....._...,: '-"c' <(:~(~\ ,.' .~:' ~ ,t '." ~.~ '. 't,'. ANN~jC$· N'ational Bureau of Standards Analysis .,' LABORATORY TESTING PROGRAM "', , .~ Test No. 4 - Glass EXamination In Test No.4, 234 laboratories were each sent two pieces of glass referred to as A and B. Participants were asked three questions: ('1) Could item A have a common origin with item B? (2) What information was developed to answer question I? (3) What methods and instrume~ts were used? Of the 234 laboratories, 124 responded with data, 49 i.ndicated they do not do glass analysis, and 61 did not respond. A tabulation of the codes for laboratories in each of these last two categories is given in Table 1. Both the supplier of the glass samples and the referee laboratories in­ dicat;e, in Tables 2 and 3, that A and B do not h?;v~ a common origin. 118 part­ icipating laboratories reported A and B could not have a common origin, 4 were inconclusive. These results are tabulated in Table 4 for each of the 124 responding laboratories. The supplier notes in Table 2 that the thickness of glass B is more uniform than the thickness of glass A. It may be noted from Tables 2 and 3 that the refractive indexes and densities of the glass B samples are also more uniform. A quantitativean~lysis was made of the two most frequently reported meth­ ods (see below) for the laboratories which reported data suitable for this purpose. Tahle 5 shows ref·ractive index and density differences between A and B. The density measurements produced greater variations than did the refractive index measuremerits. The average refractive index difference for 35 participating laboratories (those that report.ed to at least four decimal places) agrees well with the refractive index differences reported by the referee laboratories and the sample supplier. However, the density differences in Table 5 do not agree as well. Of the 12 laboratories reporting density data that can be interpreted quantitatively, two reported that A had a greater density than B, while the reverse was reported by the other 10. On the average, 2.7 methods per laboratory were reported for question 3. The relative .frequencies of the methods reported are shown in Table 6. Tables 7 and 8 show the responses to questions 2 and 3 from each laboratory. Table 9 was especially requested by the Project Advisory Committee. This annex was prepared by the La,.,. Enforcement Standards Laboratory (LESL) of N'BS, in conjunction with the NBS Laboratory Evaluation Technology Section (LETS). The anonymous test results reported by the participating forensic laboratories were analyzed and tabulated by Jeffrey Horlick and Charles Leete of LETS> and Robert Mills of LESL. This work was supported by the National Institute of Law Enforc'ement and Criminal Justice, Department of Justi~e. 4 ',' '. " . ~, t . Table 1 THE FOLLOWING LABS INDICATED THEY DO NOT DO GLASS ANALYSIS: 706 775 845 953 711 785 860 983 720 788 862 992 721 791 875 998 735 793 877 741 803 886 743 807 913 744 810 918 749 812 920 753 824 924 755 826 927 758 828 932 759 830 935 ,~, Total Labs = 49 761 841 950 o 767 844 951 THE FOLLOWING LABS DID NOT RESPOND: " 703 738 825 879 942 707 764 834 887 946 708 770 836 891 964 710 772 850 898 966 715 774 858 900 972 723 780 859 902 973 724 781 861 903 984 728 782 864 904 985 732 795 865 905 988 "":) 733 811 867 912 734 814 869 914 816 870 917 736 Total Labs == 61 737 817 871 937 G (J .e 5 ,." o • "J Table 2 . [( SUPPLIER'S CHARACTERIZATION OF SAMPLES Thickness The thickness of glass B is much more uniform than the thickness of glass A. Both are und.nted glasses. Fluorescence Glass B has tin dissolved in one of its surfaces, and thus will fluoresce when exposed to UV light. Glass A does not contain tin. Re~ractive Index Measurements made on six samples gave the following results for refractive index, ND (Sodium Line): A B 1.5167 1. 5186 1.5167 1.5185 1.5158 1.5186 1.5167 1.5185 1.5168 1.5186 1.5166 1.5186 Average: 1.51655 1.5186 Standard Deviation: 0.0004 0.00005 Density Density measurement results for six samples are as follows: A B 3 2.4860 g/cm 2.4945 g/cm 3 2.4862 2.4947 2.4821 2.49{~9 2.4876 2.4949 2.4859 2.4944 2.48g 2.4952 3 3 Average: 2.4855 g/cm 2.lf948 g/cm Standard Deviation: 0.002 0.0003 Composition A B Si0 73.37% 73.20% 2 Na 0 13.16 13.64 2 CaO 8 ..26 8.87 MgO 3.61 3.95 A1 0 1.22 0.15 2 3 K 0 0.24 0,03 2 S03 0.18 0.25 ,~, Fe 0 2 3 0.11 0.08 Total 100.15% 100.17% - 6 l:'l -' Table 3 RESULTS FROMJlIREE REFEREE L~ORATORIES Lab 1.