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The Detection and Determination of Metal Traces on Hands
J . Forens. Sci. SOC.(1974), 14, 9
The Detection and Determination of Metal Traces on Hands G. D. HUDSON and SHIRLEY J. BUTCHER Metropolitan Police Laboratory, 2 Richbell Place, London W C l N 3LA, England Methods are described for the removal of metal traces from hands by swabbing and for the subsequent quantitative analysis of copper, lead and nickel. The results of u number of surveys involving persons in a variety of occupations are given together with some case results. Introduction The theft of metal is a relatively common crime and lead or copper is usually involved. However, this laboratory has examined cases involving gold, silver, tungsten and nickel. For a number of years some police forces used a rhodizonate spot test (Feigl, 1954; Price, 1965) for the detection of lead and in 1969 a t least one force was considering the use of a n a-benzoin oxime test (Vogel, 1957) for the detection of copper. Both these tests can be made very sensitive but both suffer several grave disadvantages. The correct interpretation of colours obtained is not easy for police officers; the rhodizonate test is not sufficiently specific and neither test is quantitative. Because the results are purely qualitative it is virtually impossible to assess the evidential value of finding, for example, traces of lead on a suspect's hands, if the amount present cannot be related to that which may be acquired by the suspect going about legitimate business. This problem becomes most acute when considering copper contamination because of the everyday use of copper in coinage, brass, etc. I t therefore seemed necessary to develop a technique for the identification and quantitative removal of metal traces from the hands and to obtain sufficient background information to enable the results to be interpreted in terms of the probability of the suspect having been handling the metal in question. The work divided naturally into three sections namely: Swabbing technique. Quantitative analysis of the swabs. Surveys to determine the "normal" levels of metal contamination amongst the general population and for specific groups of workers. -
-
Swabbing Technique After trials to determine the optimum materials and method of swabbing, a complete hand swab kit was designed which is now supplied to police forces served by this laboratory. No spot test is involved and normally only swabs from these test kits will be accepted for trace metal analysis. The kits have a shelf life in excess of 6 months. The kit consists of an outer "seal-again" polythene bag containing: 1. Two seal-again bags, one labelled "test" and the other "blank", each containing a 0.2g cotton wool swab and lml of liquid soap in a plastic tube. 2. A pair of surgeon's disposable gloves. 3. A sheet of instructions. The cotton wool for the swabs is Boots Hospital quality obtained from Boots Chemists, Nottingham, England. This was selected on the grounds of reasonable cost and low metal content. Though a few police officers have criticized the swabs as being too small the selected size of 0.2g was found to be the best for subsequent extraction and analysis.
The soap used is Horton All-Purpose Liquid Soap Grade M3 obtained from Horton Cleaning Products, 43-59 Clapham Road, London SW9. Initially we used a very dilute nitric acid solution for swabbing but found that some of the people in the first survey complained of itching of the hands despite repeated washing. We then realized that the metal traces were best removed by mechanical action rather than by any solvation process. The soap merely removes the grease, allowing the metal particles to be lifted by the rubbing action of the swabs. The Scenes of Crime Officer is given explicit instruction on the use of the swabs. After washing his own hands thoroughly the officer puts on the gloves provided. He then removes the "blank" swab, adds the liquid soap to it and replaces the swab in its polythene bag. The "test" swab is then removed and the soap added. This is then used to swab both the suspect's hands, including front and side surfaces of the fingers, thumbs and palms. The swabbing is done first along the fingers and palm and then across. The swab is then placed in the "test" bag and the gloves and soap tubes discarded. The "test" and "blank" swabs are placed in the outer bag, sealed and labelled and sent to the laboratory.
Quantitative Analysis of the Swabs Extraction lOml beakers are cleaned with aqua regia and distilled water and are numbered. The "test" and "blank" swabs are numbered in the same sequence and each swab is placed in the appropriate beaker. 2ml of "Pronalysis" 2N nitric acid are added to each beaker and these are heated a t 70°C for 30 minutes on a hot plate. The swabs are repeatedly pressed with a glass rod at zero, half and full time. After cooling, the liquid is extracted through each swab with a Pasteur pipette and transferred to a 5ml volumetric flask. Approximately lml quantities of distilled water are placed in the beaker with the swab and the liquid extracted as above until the flask is almost full. It is then made up to the mark and shaken well. This liquid is solution A. Quantitative Spectrographic Analysis (spark) The equipment used was a Hilger and Watts medium quartz spectrograph with rotating electrode attachment, the spectra being recorded on Ilford longrange spectrum plates. The plate arrangement used throughout the surveys was : Duplicate standard solution burns; R.U. powder; scale; (gap of 3mm) 5 sample solution burns; (gap of 2mm) 5 sample solution burns; R.U. powder; scale. The spark technique used was: 0.lml of solution A (or appropriate standard solution) was carefully pipetted on to a clean dry cavity slide and the solution sparked (AC 15kv supply) using a Bin diam x Qin thick graphite disc as the lower electrode and a graphite rod with a 45" rounded cone as the top electrode. The disc was rotated a t 30rpm with a spark gap of 2mm. The cavity slide was adjusted so that the wheel just cleared the flat surface. When the slide was pushed in sideways the wheel then just touched the meniscus and was wetted. Sparking continued until the meniscus broke and then for a further 15 seconds giving a total exposure time of approximately 45 seconds. Standard solutions (usually 25pg/O.lml) of the metal being determined are sparked at the top of each plate-these serve as a check on the calibration curve previously constructed for the metal in question. Plates were developed using M&B Teknol (2 minutes at 65OC), fixed with M&B Amfix for 3 minutes, washed for 20 minutes and dried. For each metal to be determined quantitatively a calibration curve was constructed from a range of standard solutions. This working curve is a log-log
plot of densitometer deflection against micrograms of metal sparked. The concentration of the metal in the sample solution is calculated as follows: (i) find the average densitometer deflection for the two standard solutions=S (ii) read off the working curve deflection for the same concentration=W (iii) determine the ratio S/W (iv) read the densitometer deflection for the sample solution=X (v) (a) if S/W > 1 divide X by S/W and read off concentration from the working curve +Nyg metal (b) if S/W < 1 read off concentration N direct from working curves (vi) The amount of metal on the swab will then be N x 510.1 = N x 50yg As a n alternative to quantitative spectrographic analysis Atomic Absorption Spectroscopy can be used. Tests in this laboratory have shown that the two methods give comparable results. When analysing by AAS the swab was placed in a plastic tube and 2ml of 5% nitric acid added. The tube was then treated in an ultrasonic bath a t room temperature for 20 minutes and lOml samples analysed using a Perkin Elmer 403 instrument and the Massmann furnace HGA 70. Spectrographic detection of all metals present on the swab (arc) 2ml of solution A are placed in a 5ml beaker with 0.19 of pelletable graphite and the solution evaporated to dryness on a hot plate. The powder is packed into an open graphite electrode and arced for 30 seconds at 9A with a flat top graphite counter electrode. The open electrode is a hollow cylinder 3mm internal diameter, 0.5mm well, lcm deep and the counter electrode is a 2mm x lcm cylinder. TABLE 1 SURVEY 1: AMOUNTS O F COPPER AND LEAD FROM HANDS O F FRIENDS AND RELATIVES O F LABORATORY STAFF Occupation Housewife >>
> $9
>
Student
Copper (pg) 25 63 105 157 28 25 72 75 35 45
Lead (pg) ND 99
Other metals -
Cr
9,
3
-
-
> 9,
Patent Agent Solicitor Computer Engineer Engineer >)
Farmer
40 ND 150 50 205
-
Tech. Writer Laundress Timber Imp. Farmer Publican
Cr = chromium Ni = nickel Ba = barium
>)
2,
93
YO
ND
-
-
Copper Lead ( ~ d 25 ND 25 225 ND 25 ,, 80 ,, 25 ,, 207 30 25
+
go
Other metals
-
Ni(+)
-
-
2,
-
25 25 29 51 93
Mathematician Drawing office Optician Civil Servant Chemist Accountant Artist Sheet metal worker Park Supt. Air controller Marine Eng. Engine Inspect. Tech. Adv.*
-
Teacher
Occupation Comm. Artist Retired Insurance Agent Insurance Broker Nurse
+ : detected; not measured (<25pg) ND: not detected *: subject had been shopping for 4 hours and jingles coins in his pocket. 11
Surveys and Results Six surveys were made following the method given above. These involved 225 subjects and were: 1. Friends and relatives of laboratory staff. These were from a variety of occupations including housewives, students, teachers, various white collar and professional jobs, farmers and retired people. 2. Laboratory staff-these swabs were taken on a Monday morning as the staff entered the building. 3. Various shopkeepers, shop assistants, and post ofice counter clerks in the area surrounding the laboratory. 4. Workers at "Burch Engineeringm-light engineering workers handling various types of steel, aluminium, brass, etc. 5. Workers at "British Lead Millsu-most were process workers. 6 . Garage mechanics andpetrolpumpattendants at Ray Powell Ltd., Ilford, London. The results for each of these surveys are given in Tables 1-6. The tables are arranged to show : The occupation and, for mixed groups, sex of the subject. The levels of copper, lead and nickel found. The other metals present in significant amounts. Tables 7-9 give, respectively, the percentage occurrence, average concentration and the concentration range of copper, lead and nickel in each survey. Table 10 gives the results from some of the cases received in this laboratory in a period of about 12 months. Table 1 1 gives some case results in terms of copper and lead concentration ranges. None of the "blank" swabs in any of the surveys or case work samples showed measurable amounts of copper, lead or nickel. TABLE 2 SURVEY 2: AMOUNTS OF COPPER AND LEAD FROM HANDS OF LABORATORY STAFF Sex F
Copper (M) 55 25 25
Lead (cL~) ND
Other metals Cr -
Copper Sex M
(w)
38 43 53 100
Lead ND
Other metals
-
+
Ni, Cr -
Cr -
-
Cr Fe Ni, Cr Cr
Al, Cr Cr
-
Sn, Cr
-
Cr = chromium Al = aluminium Fe = iron
Ni = nickel Sn = tin
TABLE 3 SURVEY 3: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS OF SHOPKEEPERS AND CLERKS Copper Lead Nickel Occupation Sex (I%) (I%) Other metals Tobacconist M 350 ND 50 Ba Si A1 9, Ba Cr A1 Si F 140 Ba Cr A1 Si 39 M 270 F 185 Ba Cr A1 Si ~he2st M 175 ND A1 Si Newsagent
+ + +
>)
,1
Stationer 7,
Waitress Bank Clerk
9, 9,
Ironmonger
M M M M
Fish Fryer 3, 9,
Barman 9,
,
Barmaid 9,
Grocer $3
P.O. Counter Clerk ,>
P.O. ~ i k r k 5,
> 3, 9,
3,
Shoe repairer Florist 3, 3
Grocer 3,
Greengrocer 9,
Art ~ ' a ' l l e r ~
>, Ba = barium Si = silicon A1 = aluminium
FS-B
Cr = chromium Fe = iron Sn = tin
Sb = antimony V Zn = zinc Mn = manganese
=
vanadium
TABLE 4 SURVEY 4: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS O F MALE LIGHT ENGINEERING WORKERS Major material Cobper Lead Nickel ( W ) ( M ) (w) Other metals being handled Steel 150 ND ND Fe Ba Al Mn Si Cr ~9 147 ,, + Fe Ba A1 Mn Si Cr 207 ,, 75 Fe Ba A1 Mn Si stgel, ~l 175 ,, + Fe Ba A1 Mn Si Cr Co ND Fe Ba Zn Mn Steel, Al, brass 1250 ,, .. Fe Ba A1 Mn Si 775 .. Cast irgn Steel Steel, brass Steel steel, Al, brass Steel A<' Steel 9,
Steel, brass Steel Steel, brass Steel 99
Steel, Al, brass Steel, brass steel" >,
Cast iron Steel, brass Steel *Steel, Al, brass, bronze Steel *Steel, brass Steel, Al, brass Steel " steel, brass A1 Brass Steel, brass steel" Steel, brass Fe = iron Mn = manganese Co = cobalt Mo = molybdenum Si = silicon Zn = zinc Be = beryllium Ba = barium A1 = aluminium Cr = chromium V = vanadium * = very clean hands
TABLE 5 SURVEY 5: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS OF MALE WORKERS AT LEAD MILLS Gloves Copper Lead Nickel Worn (WLg) ( ~ g ) (M) Other metals Occupation Office worker No ND 165 ND Yes Press Operator Yes Yes Yes 2, No Foreman Pb sheet cutter No Maintenance fitter No 3, No Saw operator Yes 7, Mill operator No No Yes >9 Yes 7) Yes Saw operator Yes 9, Yes ,, Yes Handyman Saw operator No Electrician No No 9, Foreman baler Yes L.H. Baler only Yes Press operator Yes Furnaceman Fe = iron A1 = aluminium Mn = manganese
Si = silicon Cr = chromium Zn = zinc
Sn Sb Cd
= = =
tin antimony cadmium
Ba = barium
TABLE 6 SURVEY 6: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS O F GARAGE STAFF Copper Lead Nickel Occupation (I*&?) (!-%I (MI Other metals Mechanic 86 410 lOAl Fe M n B a Cr Si 9, 415 1680 32 A1 Fe Mn Ba Cr Si 3, 100 910 3 6 A l Fe M n B a Cr Si 12 A1 Fe Mn Ba Cr Si 47 720 29 Petrol pump att. 35 58 7 A1 9, 121 93 2 4 A l A1 = aluminium Fe = iron Mn = manganese
Ba = barium Cr = chromium Si = silicon
TABLE 7 PERCENTAGE MEASURABLE OCCURRENCE IN SURVEY Survey Copper Lead Nickel Friends and Relatives 1 96 8 2 Lab. Staff 2 64 2 0 Shopkeepers, clerks 3 90 10 16 Light engineering 4 100 5 20 Lead mill 5 80 100 0 Mechanics, pump att. 6 100 100 100
TABLE 8 AVERAGE O F MEASURABLE AMOUNTS OF METAL No. in copper Lead Survey pg No. Sex pg Survey No. Sex 1 49 (1) 24 M 130 4 M 60 3 M 60 '2' 0 F 53 23 M 70 1 M 120 F 40 0 F 11
;; FM
No. 1 0 0 0 0 7 1 9 0 4
Nickel sex
(1) Includes tech. adviser survey 1. (2) Exludes tech. adviser survey 1. (3) Includes mechanics only.
TABLE 9 Survey l*
2 3 4 5 6**
METAL CONCENTRATION RANGE (pg) Sex Copper Lead Nickel M <25-270 ND-70 ND F <25-210 ND ND ND-120 ND t25-330 M F ND-80 ND ND M ND-750 ND-200 ND-90 F ND-550 ND-100 ND-60 A4 50-3600 ND-200 ND-260 M ND-1100 160-30000 ND M 35-4 10 60-1680 10-40 ND
* **
= = =
not detected tech. adviser survey 1 not included includes 1 female
M
160
TABLE 10 SOME CASE RESULTS (IN DATE ORDER) Copper Lead Nickel Rd. Metal involved in theft (pg) (pg) (w) 1 Lead from roof 0 3, 2 1175 3 Copper scrap 50 4 Brass fittings 70 33 <50 5 Scrap metal 87 , <50 29 125 6 Copper cable 225 3) 305 130 7 Lead from roof 1200 8 470 9 3, 1900 10 99 1550 11 700 900 12 1400 13 1400 14 15 Copper piping 80 16 Copper tube and lead scrap 220 0 205 0 17 Scrap metal 175 <25 3, 60 <25 120 <25 18 Lead &om roof 1500 9, 310 5000 50 5000 9, 19 Copper cable 700 625 20 Lead Gpe 110 <80 9, 200 <80 9 340 <80 7, 200) 625 28 9 550 9, 850 >)
>)
>)
TABLE 11 CASE RESULTS 0 Copper Lead
-
5
No. of swabs with concentration (pg) 100-200 200-500 500-1000 1000 9 10 2 3 8 10 15
Total No. swabs 36 48
Avmage Highest corn. concn. 170 700 980 >5000
Discussion Lead The results for surveys 1-4 indicate that little difficulty should be encountered in interpreting case results for persons suspected of lead theft provided the position as regards special groups of workers is taken into account. With regard to the general levels of lead found on peoples' hands perhaps the most surprising result was the relatively high levels found on the hands of garage mechanics (410-1680pg). These were considerably higher then those found on the petrol pump attendants (58-93pg) and could be derived from lead based greases. The very high levels for many of the workers in British Lead Mills give some idea of the levels to be expected for persons handling lead constantly. Even the operators who were wearing gloves a t the time of the survey had up to 12,500pg on their hands. It should also be noted that a reasonably thorough washing of the hands will remove most of the lead. A swab from the hands of a subject who passed a lead rod through his hands for several minutes yielded 1500pg Pb. He then washed his hands, handled the lead for a comparable time and washed his hands again. The swab from his hands then yielded only 100pg Pb. Thus if lead is not found the suspect could still have been handling the metal if he has been able to wash his hands after the offence. Copper It is obvious from the survey results that the interpretation of results for copper on test swabs requires considerable caution. All the subjects in all 6 surveys had detectable amounts of copper on their hands though in a few cases the amount was not measured, i.e. was less than 25pg. Frequently, though not invariably, nickel was also present in detectable amounts when the level of copper was relatively high. This presumably indicates that the copper in those cases was derived from coinage. The results for the Technical Adviser in survey 1 (1000pg Cu, 160pg Ni) indicate the levels that can be expected from persons handling coins over an extended period. Regrettably we were not able to arrange a survey of bus conductors or people in similar occupations. If levels of copper of the order of 500pg or more are found on test swabs with nickel absent or present in only trace amounts then one would probably be justified in assessing the copper result as significant.
Acknowledgements We would like to express our thanks to Burch Engineering, British Lead Mills and Ray Powell Ltd., for their co-operation in allowing 3 of the surveys to be made. We are also grateful to Mr. D. Neylan for advice and assistance with the quantitative spectrography, to Mr. M. Annis for much help with the practical work and to Dr. B. N. Dailly for organizing two of the surveys.
References FEIGL,F., 1954, Spot Tests-Inorganic Application, 4th edn, p. 69. PRICE,G., 1965, J. Forens. Sci. Soc., 5, 199. VOGEL.A., 1957, Qualitative Inorganic Analysis. 4th edn. p. 227.
The Detection and Determination of Metal Traces on Hands G. D. HUDSON and SHIRLEY J. BUTCHER Metropolitan Police Laboratory, 2 Richbell Place, London W C l N 3LA, England Methods are described for the removal of metal traces from hands by swabbing and for the subsequent quantitative analysis of copper, lead and nickel. The results of u number of surveys involving persons in a variety of occupations are given together with some case results. Introduction The theft of metal is a relatively common crime and lead or copper is usually involved. However, this laboratory has examined cases involving gold, silver, tungsten and nickel. For a number of years some police forces used a rhodizonate spot test (Feigl, 1954; Price, 1965) for the detection of lead and in 1969 a t least one force was considering the use of a n a-benzoin oxime test (Vogel, 1957) for the detection of copper. Both these tests can be made very sensitive but both suffer several grave disadvantages. The correct interpretation of colours obtained is not easy for police officers; the rhodizonate test is not sufficiently specific and neither test is quantitative. Because the results are purely qualitative it is virtually impossible to assess the evidential value of finding, for example, traces of lead on a suspect's hands, if the amount present cannot be related to that which may be acquired by the suspect going about legitimate business. This problem becomes most acute when considering copper contamination because of the everyday use of copper in coinage, brass, etc. I t therefore seemed necessary to develop a technique for the identification and quantitative removal of metal traces from the hands and to obtain sufficient background information to enable the results to be interpreted in terms of the probability of the suspect having been handling the metal in question. The work divided naturally into three sections namely: Swabbing technique. Quantitative analysis of the swabs. Surveys to determine the "normal" levels of metal contamination amongst the general population and for specific groups of workers. -
-
Swabbing Technique After trials to determine the optimum materials and method of swabbing, a complete hand swab kit was designed which is now supplied to police forces served by this laboratory. No spot test is involved and normally only swabs from these test kits will be accepted for trace metal analysis. The kits have a shelf life in excess of 6 months. The kit consists of an outer "seal-again" polythene bag containing: 1. Two seal-again bags, one labelled "test" and the other "blank", each containing a 0.2g cotton wool swab and lml of liquid soap in a plastic tube. 2. A pair of surgeon's disposable gloves. 3. A sheet of instructions. The cotton wool for the swabs is Boots Hospital quality obtained from Boots Chemists, Nottingham, England. This was selected on the grounds of reasonable cost and low metal content. Though a few police officers have criticized the swabs as being too small the selected size of 0.2g was found to be the best for subsequent extraction and analysis.
The soap used is Horton All-Purpose Liquid Soap Grade M3 obtained from Horton Cleaning Products, 43-59 Clapham Road, London SW9. Initially we used a very dilute nitric acid solution for swabbing but found that some of the people in the first survey complained of itching of the hands despite repeated washing. We then realized that the metal traces were best removed by mechanical action rather than by any solvation process. The soap merely removes the grease, allowing the metal particles to be lifted by the rubbing action of the swabs. The Scenes of Crime Officer is given explicit instruction on the use of the swabs. After washing his own hands thoroughly the officer puts on the gloves provided. He then removes the "blank" swab, adds the liquid soap to it and replaces the swab in its polythene bag. The "test" swab is then removed and the soap added. This is then used to swab both the suspect's hands, including front and side surfaces of the fingers, thumbs and palms. The swabbing is done first along the fingers and palm and then across. The swab is then placed in the "test" bag and the gloves and soap tubes discarded. The "test" and "blank" swabs are placed in the outer bag, sealed and labelled and sent to the laboratory.
Quantitative Analysis of the Swabs Extraction lOml beakers are cleaned with aqua regia and distilled water and are numbered. The "test" and "blank" swabs are numbered in the same sequence and each swab is placed in the appropriate beaker. 2ml of "Pronalysis" 2N nitric acid are added to each beaker and these are heated a t 70°C for 30 minutes on a hot plate. The swabs are repeatedly pressed with a glass rod at zero, half and full time. After cooling, the liquid is extracted through each swab with a Pasteur pipette and transferred to a 5ml volumetric flask. Approximately lml quantities of distilled water are placed in the beaker with the swab and the liquid extracted as above until the flask is almost full. It is then made up to the mark and shaken well. This liquid is solution A. Quantitative Spectrographic Analysis (spark) The equipment used was a Hilger and Watts medium quartz spectrograph with rotating electrode attachment, the spectra being recorded on Ilford longrange spectrum plates. The plate arrangement used throughout the surveys was : Duplicate standard solution burns; R.U. powder; scale; (gap of 3mm) 5 sample solution burns; (gap of 2mm) 5 sample solution burns; R.U. powder; scale. The spark technique used was: 0.lml of solution A (or appropriate standard solution) was carefully pipetted on to a clean dry cavity slide and the solution sparked (AC 15kv supply) using a Bin diam x Qin thick graphite disc as the lower electrode and a graphite rod with a 45" rounded cone as the top electrode. The disc was rotated a t 30rpm with a spark gap of 2mm. The cavity slide was adjusted so that the wheel just cleared the flat surface. When the slide was pushed in sideways the wheel then just touched the meniscus and was wetted. Sparking continued until the meniscus broke and then for a further 15 seconds giving a total exposure time of approximately 45 seconds. Standard solutions (usually 25pg/O.lml) of the metal being determined are sparked at the top of each plate-these serve as a check on the calibration curve previously constructed for the metal in question. Plates were developed using M&B Teknol (2 minutes at 65OC), fixed with M&B Amfix for 3 minutes, washed for 20 minutes and dried. For each metal to be determined quantitatively a calibration curve was constructed from a range of standard solutions. This working curve is a log-log
plot of densitometer deflection against micrograms of metal sparked. The concentration of the metal in the sample solution is calculated as follows: (i) find the average densitometer deflection for the two standard solutions=S (ii) read off the working curve deflection for the same concentration=W (iii) determine the ratio S/W (iv) read the densitometer deflection for the sample solution=X (v) (a) if S/W > 1 divide X by S/W and read off concentration from the working curve +Nyg metal (b) if S/W < 1 read off concentration N direct from working curves (vi) The amount of metal on the swab will then be N x 510.1 = N x 50yg As a n alternative to quantitative spectrographic analysis Atomic Absorption Spectroscopy can be used. Tests in this laboratory have shown that the two methods give comparable results. When analysing by AAS the swab was placed in a plastic tube and 2ml of 5% nitric acid added. The tube was then treated in an ultrasonic bath a t room temperature for 20 minutes and lOml samples analysed using a Perkin Elmer 403 instrument and the Massmann furnace HGA 70. Spectrographic detection of all metals present on the swab (arc) 2ml of solution A are placed in a 5ml beaker with 0.19 of pelletable graphite and the solution evaporated to dryness on a hot plate. The powder is packed into an open graphite electrode and arced for 30 seconds at 9A with a flat top graphite counter electrode. The open electrode is a hollow cylinder 3mm internal diameter, 0.5mm well, lcm deep and the counter electrode is a 2mm x lcm cylinder. TABLE 1 SURVEY 1: AMOUNTS O F COPPER AND LEAD FROM HANDS O F FRIENDS AND RELATIVES O F LABORATORY STAFF Occupation Housewife >>
> $9
>
Student
Copper (pg) 25 63 105 157 28 25 72 75 35 45
Lead (pg) ND 99
Other metals -
Cr
9,
3
-
-
> 9,
Patent Agent Solicitor Computer Engineer Engineer >)
Farmer
40 ND 150 50 205
-
Tech. Writer Laundress Timber Imp. Farmer Publican
Cr = chromium Ni = nickel Ba = barium
>)
2,
93
YO
ND
-
-
Copper Lead ( ~ d 25 ND 25 225 ND 25 ,, 80 ,, 25 ,, 207 30 25
+
go
Other metals
-
Ni(+)
-
-
2,
-
25 25 29 51 93
Mathematician Drawing office Optician Civil Servant Chemist Accountant Artist Sheet metal worker Park Supt. Air controller Marine Eng. Engine Inspect. Tech. Adv.*
-
Teacher
Occupation Comm. Artist Retired Insurance Agent Insurance Broker Nurse
+ : detected; not measured (<25pg) ND: not detected *: subject had been shopping for 4 hours and jingles coins in his pocket. 11
Surveys and Results Six surveys were made following the method given above. These involved 225 subjects and were: 1. Friends and relatives of laboratory staff. These were from a variety of occupations including housewives, students, teachers, various white collar and professional jobs, farmers and retired people. 2. Laboratory staff-these swabs were taken on a Monday morning as the staff entered the building. 3. Various shopkeepers, shop assistants, and post ofice counter clerks in the area surrounding the laboratory. 4. Workers at "Burch Engineeringm-light engineering workers handling various types of steel, aluminium, brass, etc. 5. Workers at "British Lead Millsu-most were process workers. 6 . Garage mechanics andpetrolpumpattendants at Ray Powell Ltd., Ilford, London. The results for each of these surveys are given in Tables 1-6. The tables are arranged to show : The occupation and, for mixed groups, sex of the subject. The levels of copper, lead and nickel found. The other metals present in significant amounts. Tables 7-9 give, respectively, the percentage occurrence, average concentration and the concentration range of copper, lead and nickel in each survey. Table 10 gives the results from some of the cases received in this laboratory in a period of about 12 months. Table 1 1 gives some case results in terms of copper and lead concentration ranges. None of the "blank" swabs in any of the surveys or case work samples showed measurable amounts of copper, lead or nickel. TABLE 2 SURVEY 2: AMOUNTS OF COPPER AND LEAD FROM HANDS OF LABORATORY STAFF Sex F
Copper (M) 55 25 25
Lead (cL~) ND
Other metals Cr -
Copper Sex M
(w)
38 43 53 100
Lead ND
Other metals
-
+
Ni, Cr -
Cr -
-
Cr Fe Ni, Cr Cr
Al, Cr Cr
-
Sn, Cr
-
Cr = chromium Al = aluminium Fe = iron
Ni = nickel Sn = tin
TABLE 3 SURVEY 3: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS OF SHOPKEEPERS AND CLERKS Copper Lead Nickel Occupation Sex (I%) (I%) Other metals Tobacconist M 350 ND 50 Ba Si A1 9, Ba Cr A1 Si F 140 Ba Cr A1 Si 39 M 270 F 185 Ba Cr A1 Si ~he2st M 175 ND A1 Si Newsagent
+ + +
>)
,1
Stationer 7,
Waitress Bank Clerk
9, 9,
Ironmonger
M M M M
Fish Fryer 3, 9,
Barman 9,
,
Barmaid 9,
Grocer $3
P.O. Counter Clerk ,>
P.O. ~ i k r k 5,
> 3, 9,
3,
Shoe repairer Florist 3, 3
Grocer 3,
Greengrocer 9,
Art ~ ' a ' l l e r ~
>, Ba = barium Si = silicon A1 = aluminium
FS-B
Cr = chromium Fe = iron Sn = tin
Sb = antimony V Zn = zinc Mn = manganese
=
vanadium
TABLE 4 SURVEY 4: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS O F MALE LIGHT ENGINEERING WORKERS Major material Cobper Lead Nickel ( W ) ( M ) (w) Other metals being handled Steel 150 ND ND Fe Ba Al Mn Si Cr ~9 147 ,, + Fe Ba A1 Mn Si Cr 207 ,, 75 Fe Ba A1 Mn Si stgel, ~l 175 ,, + Fe Ba A1 Mn Si Cr Co ND Fe Ba Zn Mn Steel, Al, brass 1250 ,, .. Fe Ba A1 Mn Si 775 .. Cast irgn Steel Steel, brass Steel steel, Al, brass Steel A<' Steel 9,
Steel, brass Steel Steel, brass Steel 99
Steel, Al, brass Steel, brass steel" >,
Cast iron Steel, brass Steel *Steel, Al, brass, bronze Steel *Steel, brass Steel, Al, brass Steel " steel, brass A1 Brass Steel, brass steel" Steel, brass Fe = iron Mn = manganese Co = cobalt Mo = molybdenum Si = silicon Zn = zinc Be = beryllium Ba = barium A1 = aluminium Cr = chromium V = vanadium * = very clean hands
TABLE 5 SURVEY 5: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS OF MALE WORKERS AT LEAD MILLS Gloves Copper Lead Nickel Worn (WLg) ( ~ g ) (M) Other metals Occupation Office worker No ND 165 ND Yes Press Operator Yes Yes Yes 2, No Foreman Pb sheet cutter No Maintenance fitter No 3, No Saw operator Yes 7, Mill operator No No Yes >9 Yes 7) Yes Saw operator Yes 9, Yes ,, Yes Handyman Saw operator No Electrician No No 9, Foreman baler Yes L.H. Baler only Yes Press operator Yes Furnaceman Fe = iron A1 = aluminium Mn = manganese
Si = silicon Cr = chromium Zn = zinc
Sn Sb Cd
= = =
tin antimony cadmium
Ba = barium
TABLE 6 SURVEY 6: AMOUNTS O F COPPER, LEAD AND NICKEL FROM HANDS O F GARAGE STAFF Copper Lead Nickel Occupation (I*&?) (!-%I (MI Other metals Mechanic 86 410 lOAl Fe M n B a Cr Si 9, 415 1680 32 A1 Fe Mn Ba Cr Si 3, 100 910 3 6 A l Fe M n B a Cr Si 12 A1 Fe Mn Ba Cr Si 47 720 29 Petrol pump att. 35 58 7 A1 9, 121 93 2 4 A l A1 = aluminium Fe = iron Mn = manganese
Ba = barium Cr = chromium Si = silicon
TABLE 7 PERCENTAGE MEASURABLE OCCURRENCE IN SURVEY Survey Copper Lead Nickel Friends and Relatives 1 96 8 2 Lab. Staff 2 64 2 0 Shopkeepers, clerks 3 90 10 16 Light engineering 4 100 5 20 Lead mill 5 80 100 0 Mechanics, pump att. 6 100 100 100
TABLE 8 AVERAGE O F MEASURABLE AMOUNTS OF METAL No. in copper Lead Survey pg No. Sex pg Survey No. Sex 1 49 (1) 24 M 130 4 M 60 3 M 60 '2' 0 F 53 23 M 70 1 M 120 F 40 0 F 11
;; FM
No. 1 0 0 0 0 7 1 9 0 4
Nickel sex
(1) Includes tech. adviser survey 1. (2) Exludes tech. adviser survey 1. (3) Includes mechanics only.
TABLE 9 Survey l*
2 3 4 5 6**
METAL CONCENTRATION RANGE (pg) Sex Copper Lead Nickel M <25-270 ND-70 ND F <25-210 ND ND ND-120 ND t25-330 M F ND-80 ND ND M ND-750 ND-200 ND-90 F ND-550 ND-100 ND-60 A4 50-3600 ND-200 ND-260 M ND-1100 160-30000 ND M 35-4 10 60-1680 10-40 ND
* **
= = =
not detected tech. adviser survey 1 not included includes 1 female
M
160
TABLE 10 SOME CASE RESULTS (IN DATE ORDER) Copper Lead Nickel Rd. Metal involved in theft (pg) (pg) (w) 1 Lead from roof 0 3, 2 1175 3 Copper scrap 50 4 Brass fittings 70 33 <50 5 Scrap metal 87 , <50 29 125 6 Copper cable 225 3) 305 130 7 Lead from roof 1200 8 470 9 3, 1900 10 99 1550 11 700 900 12 1400 13 1400 14 15 Copper piping 80 16 Copper tube and lead scrap 220 0 205 0 17 Scrap metal 175 <25 3, 60 <25 120 <25 18 Lead &om roof 1500 9, 310 5000 50 5000 9, 19 Copper cable 700 625 20 Lead Gpe 110 <80 9, 200 <80 9 340 <80 7, 200
>)
>)
TABLE 11 CASE RESULTS 0 Copper Lead
-
5
No. of swabs with concentration (pg) 100-200 200-500 500-1000 1000 9 10 2 3 8 10 15
Total No. swabs 36 48
Avmage Highest corn. concn. 170 700 980 >5000
Discussion Lead The results for surveys 1-4 indicate that little difficulty should be encountered in interpreting case results for persons suspected of lead theft provided the position as regards special groups of workers is taken into account. With regard to the general levels of lead found on peoples' hands perhaps the most surprising result was the relatively high levels found on the hands of garage mechanics (410-1680pg). These were considerably higher then those found on the petrol pump attendants (58-93pg) and could be derived from lead based greases. The very high levels for many of the workers in British Lead Mills give some idea of the levels to be expected for persons handling lead constantly. Even the operators who were wearing gloves a t the time of the survey had up to 12,500pg on their hands. It should also be noted that a reasonably thorough washing of the hands will remove most of the lead. A swab from the hands of a subject who passed a lead rod through his hands for several minutes yielded 1500pg Pb. He then washed his hands, handled the lead for a comparable time and washed his hands again. The swab from his hands then yielded only 100pg Pb. Thus if lead is not found the suspect could still have been handling the metal if he has been able to wash his hands after the offence. Copper It is obvious from the survey results that the interpretation of results for copper on test swabs requires considerable caution. All the subjects in all 6 surveys had detectable amounts of copper on their hands though in a few cases the amount was not measured, i.e. was less than 25pg. Frequently, though not invariably, nickel was also present in detectable amounts when the level of copper was relatively high. This presumably indicates that the copper in those cases was derived from coinage. The results for the Technical Adviser in survey 1 (1000pg Cu, 160pg Ni) indicate the levels that can be expected from persons handling coins over an extended period. Regrettably we were not able to arrange a survey of bus conductors or people in similar occupations. If levels of copper of the order of 500pg or more are found on test swabs with nickel absent or present in only trace amounts then one would probably be justified in assessing the copper result as significant.
Acknowledgements We would like to express our thanks to Burch Engineering, British Lead Mills and Ray Powell Ltd., for their co-operation in allowing 3 of the surveys to be made. We are also grateful to Mr. D. Neylan for advice and assistance with the quantitative spectrography, to Mr. M. Annis for much help with the practical work and to Dr. B. N. Dailly for organizing two of the surveys.
References FEIGL,F., 1954, Spot Tests-Inorganic Application, 4th edn, p. 69. PRICE,G., 1965, J. Forens. Sci. Soc., 5, 199. VOGEL.A., 1957, Qualitative Inorganic Analysis. 4th edn. p. 227.