Neutron Activation Gulf Atomic Group Gunshot Residue
Studies of gunshot residue on ResearchGate, neutron activation analysis and compared with the composition of deposits obtained by primer firings alone.
J Forensic Sci, Oct. 1974, Vol. 19, No. 4
S. S. Krishnan,1 Ph.D. S. S. Krishnan, 1 P h. D.
Detection of Gunshot Residue on the Hands by Detection Gunshot Residue on the Hands by Neutron Activation and Atomic Absorption Neutron Activation and Atomic Absorption
Analysis Analysis
Neutron activation analysis NAA for antimony and barium has been described as the Neutron analysis NAA for antimony and barium has been described as the most effective technique for the detection of gunshot residues on the hands of a suspect effective technique for the detection of gunshot residues on the hands of a suspect 1,2. The method, however, is not used routinely for aa number of reasons. Among the 1,2. The method, however, is not used routinely for number of reasons. Among the reasons are the complex nature of the statistical treatment of the data and the difficulty reasons are the complex nature of the statistical treatment of the data and difficulty experienced by individual laboratories of collecting the voluminous background data experienced by individual laboratories of collecting the voluminous background data required for these calculations. One of the important aspects of the technique is that the these calculations. One of the important aspects of the technique is that the
sample has to be collected with extreme care so that the contamination is minimal. sample has to be collected with extreme care so that the contamination is minimal.
Because the amount-s of the elements analyzed are at microgram levels, specially designed designed Because the amounts microgram levels,
proceduresand training are required to be able to collect the samples without procedures and training are required to be able to collect the samples without
contamination. The existing techniques, such as paraffin lift and cotton swabbing, are contamination. The existing techniques, such as paraffin lift and cotton swabbing, are found be unsatisfactory in this respect. By taking repeated samples from hands by found to be unsatisfactory in this respect. By taking repeated samples from hands by these procedures, it was found that three or four collections are required for complete these procedures, it was found that three four collections are required for complete removal of the trace elements. Thus, a single collection by these methods is not removal of the trace elements. Thus, a single collectionby these methods is not therefore, any subsequent quantitative, and therefore, any subsequent calculation would be in error. would be in error. Neutron activation analysis is not effective in detecting lead, which is one of Neutron activation analysis is not effective in detecting lead, which is one of the constituents of leakage residues. Hence, method such as atomic absorption important constituents of leakage residues. Hence, aa method such as atomic absorption spectrometry AAS must be used in addition to NAA for this analysis. Preliminary spectrometry AAS must be used in addition NAA for this analysis. Preliminary experiments had shown that AAS is not a suitable technique for antimony and barium experiments had shown that AAS is not suitable technique for antimony and barium analysis in this application. With flame atomization, the amounts actually encountered analysis in this application. With flame atomization, the amounts actually encountered in some samples are below the detection limits. When aa heated graphite atomizer is some samples are below the detection limits. When heated graphite atomizer is used, the detection limits are adequate but the precision is poor. Further research efforts detection the precision poor. research efforts therefore, necessary before AAS can be used routinely for all three elements. Thus, are, therefore, necessary before AAS can be used routinely for all three elements. Thus, the results reported by Green and Sauve 3 and Renshaw et al 4 could not the results reported by Green and Sauve 3 and Renshaw et al 4 could not be or confirmed attempts using limited given. reproduced or confirmed by our attempts using the limited details given.
Experimental
Neutron Activation Analysis Neutron Activation Analysis
The irradiation is done in a nuclear reactor yielding a thermal neutron flux of approxiapproxiThe is done in a nuclear reactor yielding thermal neutron mately 1O neutrons s-a cm -z. The radioactivity is measured with 3 by 3-in. 76.2 by mately 1013neutrons s1 cm2. The radioactivity is measured with aa 3 by 3-in. 76.2 by
76.2-mm sodium iodide scintillation detector connected to 400 analyzer. 76.2-mm sodium iodide scintillation detector connected to aa 400 channel analyzer.
Received for publication 15 Nov. 1973; revised manuscript received 7 Feb. 1974; accepted for Received for 15 Nov. 1973; revised manuscript received 7 Feb. 1974; accepted for publication 11 Feb. 1974. publication 11 Feb. 1974. JChemistry Section, The Centre of Forensic Sciences, Toronto, Chemistry Section, The Centre of Forensic Sciences, Toronto, Ontario, Canada.
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JOURNAL OF FORENSIC SCIENCES JOURNAL OF FORENSIC SCIENCES
Atomic Absorption Spectrophotometry Spectrophotometry
The measurementsare made using a Perkin-Elmer 303 instrument with a The measurements are made using Perkin-Elmer 303 instrument with
Perkin-ElmerHollow Cathode lamp and aa three-slot Boling burner. The lead is Perkin-Elmer Hollow Cathode lamp and three-slot Boling burner. The lead
procedure 5. determined by a standard procedure 5.
Reagents and Chemicals Chemicals
The reagents and chemicals used were of Analar grade. Double-distilled and The reagents and chemicals used were Analar grade. Double-distilled and
deionized water was used. water was used.
Collection Sample Collection
The method of sample collection in this work is based on washing the hand with M The method of sample collection in this work is based on washing the hand with 11M nitric acid. The kit supplied for this purpose consists of a plastic bottle containing 50 nitric acid. kit supplied for this purpose consists of plastic containing 50 ml of 1 M nitric acid and an acid-cleaned plastic bag. The acid from the bottle is ml 1 M nitric acid and an acid-cleaned plastic bag. The acid from the bottle carefully poured into the bag without touching its inside. The suspect s hand is inserted carefully poured into the bag without touching its inside. The suspect s hand is inserted into the bag, shaken for 10 to 15 seconds to wet all parts of the hand, and removed. The the bag, shaken for 10 to 15 seconds to wet all parts of the hand, and removed. The acid is poured back into the bottle and sent to the laboratory for analysis. It is found acid poured back bottle and sent to the laboratory for analysis. It found that aa single wash as described above completely removes the entire residue from the single wash as described above completely removes the entire residue from hand. Further, because the procedure takes only a few seconds and during that time only Further, because the procedure takes only few seconds and during that time only the outsides of the bags are handled, the problem of contamination is minimal. The outsides bags are handled, the problem of contamination is minimal. The liquid is concentrated by freeze-drying,since it was observed that antimony is retained concentrated freeze-drying, since it was observed that antimony is retained by the container walls if heated. If freeze-dryingequipment is not available, it may be container walls heated. freeze-drying equipment is not available, it may be possible to extract the metals in an organic medium which can then be evaporated at possible to extract the metals in an organic medium which can then be evaporated at room temperature. The analysis was done by the procedure shown in Fig. 1. The analysis was done by the procedure shown in Fig. 1.
Results and Discussion Diseusslon
Amounts of Trace Elements Deposited Elements Deposited
In order to decide whether or not a person has fired a gun, six factors are considered. order decide whether or not a person has fired gun, six factors are considered. These are the absolute amounts of lead, antimony, and barium and the ratios of each of These are the absolute amounts of lead, antimony, and barium and the ratios of each of these amounts on one hand compared with the other. The data obtained are summarized compared with the other. The data summarized in Tables 1 and 2. Tables The amounts of lead, antimony, and barium, as well as the ratios, were found to be amounts of lead, antimony, and barium, as well as the ratios, were found to be higher on hands that have fired a gun than on normal hands. There is, however, quite aa on hands that have fired a gun than on normal hands. There is, however, quite spread in the values with some overlap between the normal blank values and those spread the values with some overlap between the normal blank values and those obtained after firing. Thus, it seems that the concept of establishing deposit on the obtained after firing. Thus, it seems that the concept of establishing aa deposit on the after a firing is meaningful, although 100 percent success cannot be expected on hand after a firing is meaningful, although 100 percent success cannot be expected on account of this overlap of data. Treatment of Data Having obtained analytical data for hand washes of normal hands and those that have Having obtained analytical data for hand washes of normal hands and those that have
fired weapon, it is necessary to develop some criteria for establishing with some fired a weapon, it is necessary to develop some criteria for establishing with some
certainty whether or not a gun has been fired. All the variables involved in the study are whether or not a has fired. the variables involved in the study are completely known, and the few known are of random nature. Thus, the treatment not completelyknown, and the few known are of aarandom nature. Thus, the treatment has to be of a statistical nature. Schlesinger et al 2 have reported procedure of data has to be of a statistical nature. Schlesinger et al 2 have reported aa procedure based bivariate statistical model. However, their procedure is difficult to based on the bivariate normal statistical model. However,their procedure is difficult to apply directly to this or other worker s data for several reasons. First of all, it would be apply directly to this or other worker s data for several reasons. First of all, it would be
necessary to collect voluminous amount of background data, particularly on necessaryto collect a voluminous amount of background data, particularly on occupational levels. Further, their method utilizes antimony and barium values only and occupational levels. Further, their method utilizes antimony and barium values only and
KRISHNAN ON GUNSHOT RESIDUE DETECTION KRISHNAN ON GUNSHOT RESIDUE DETECTION
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Collect the liquid sample into a Collect the liquid sample into a tumbler shaped pyrex beaker tumbler shaped pyrex beaker
Freeze dry the sample Freeze the sample
Take the sample into 2 of IM nitric acid Take the sample into 2 ml of 1M nitric acid
.4,
Take 0.5 nil and estimate 0.5 ml and estimate
lead using atomic absorplead using atomic absorption spectrophotometry tion spectrophotometry
Freeze dry the 1.5 nil and dry the 1.5 ml take in 1 or 2 drops 1M take I or drops IM nitric acid. Transfer it nitric acid. Transfer it along with washings into a along with washings into a spectrographic graphite cup spectrographic graphite cup or similar container. Air or similar container. Air or fre zze dry. or f r e e e d r y.
Irradiate the cup in therIrradiate cup in thermal neutron flux in a reactor mal neutron flux reactor for approximately 12 hours for approximately 12 hours at flux of aporoximately flux approximately 101Jn cm-2 sec-1. 10in cm2 sec1.
4f
Wash the sample and make up Wash the sample up to 10 ml to 10
Take one 5 ml portion Take 5 and a d i o c h c a l l y and rradiochcal1y separate separate Ba as Ba SO 4. Estimate Ba S0. Estimate barium content by barium content comparison with stancomparison with standard. dard.
tportion
__ 1 L
I
Let the other 5 ml the other 5 ml portion stand until portion stand all the radioall the radioactivities except activities except Sb122 has decayed Sb122 has decayed to a large extent, to large extent. Count the Sb122 and Count the Sb 1LL and estimate the antimony estimate the antimony content comparison content by comparison with standards. standards.
FIG. 1--Analytical procedure. 1--Analytical procedure.
no account is taken of the amounts of lead or the ratios of concentration on one hand to no account is taken of the amounts of lead or the ratios of concentration on one hand to concentration on the other. It is difficult to simplify sufficiently their statistical procedure concentration on other. It is difficult simplify sufficiently their statistical procedure for use in actual criminal case investigationand to be able to point out the relevance and use actual criminal case investigation and to be able to point out the relevance and peculiarity, if any, of the sample in particular criminal case. Thus, the high ratios of peculiarity, if any, of the sample in aa particular criminal case. Thus, the high ratios of
amounts on one hand to amounts on the other are perhaps more valuable evidence at amounts on one hand to amounts on the other are perhaps more valuable evidence at
face value in a criminalcase than to be able to state in a general manner that the face value in a criminal case than to be able to state in a general manner that the
absolute levels found are statistically significant. The statistical calculations are difficult absolute levels found are statistically significant. The statistical calculations are difficult for a jury to understand. jury to understand. In this work, an alternative method of treatment of data has been developed with the this work, an alternative method of treatment data has been developed with the above difficulties in mind. The three absolute concentration values and the three ratios above difficulties in mind. The three absolute concentration values and the three ratios
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TABLE 1--Range of amounts of trace elements found on normal hands. 1--Range amounts elements on normal hands.
Range of Amounts of Amounts Amount on Amount on Right Hand/ Right Hand/ Amount on Either Hand, Either Hand, Left Hand g pg
Frequent Value Most Frequent Value Amount on on Amount on Amount Right Right Hand/ Amount on Either Hand, Left Hand g pg 10 5 to 10 0.02
Element
Lead
Subjects a Subjectsa
30 23 12
Antimony Barium
5 to 95 to 95 0.003 to 0.94 0.003 0.07 to 0.27
0.8/2.2 0.6/2.8 0.8/1.5 0.8/1.5
0.2
1.0/1.4 1.0/1.4 0.6/1.0 0.6/1.0 0.8/1.0 0.8/1.0
U Occupation: forensic science laboratory workers. a Occupation: laboratory workers.
2--Range elements after shooting on hands not cleaned TABLE 2--Range of amounts of trace elements found after shooting on hands not cleaned amounts prior to shooting: weapon--. 38 revolver, ammunition--Dominion. prior to shooting: weapon--. 38 revolver, ammunition--Dominion.
Range of Amounts Range
Firing Hand, g pg Nonfiring Hand, Hand, /ag pg
MoSt Frequent Value Most
Hand. Hand/
Nonfiring Hand
Firing
Shots Fired a Fired a
Firing Hand, /ag pg
Nonfiring Nonfiring Hand, / g pg
Firing Hand. Hand/ Nonfiring Nonfiring Hand
30 30
19 20
13--326 10-110 13-326 0.35-5.9 0.05-0.5 0.35-5.9 0.19-1.4 0.05-0.45 0.19-1.4 0.05-0.45
1.0/12.4 1.0/12.4 1.0/7.0
0.4/5.5 0.4/5.5
35-85 0.1-0.3 0.25-0.3
10-40
0.2 0.2
0.05-0.15
1.5/2.0 1.5/3.5 1.5/2.5
Occupation of subjects: forensic science laboratory workers. a Occupation of subjects: forensic science laboratory workers.
all important, but not necessarily of equal value. By reference to the frequency distriare all important, but not necessarily of equal value. By reference to the frequency distri-
bution curve and particularly to the most probable values, statistical weights were bution curve and particularly to the most probable values, statistical weights were
attached to the different absolute amounts and the ratios. These were added to obtain aa attached to the different absolute amounts and the ratios. These were added to obtain combined weight called the point count total for particular analysis. Approximately a combined weight called the point count total for a particular analysis. Approximately a dozen combinations of these weights were tried, and the set of weights which gave the dezen combinations of these weights were tried, and the set of weights which gave the best dfft rentiation of the point count index between a anormal pair of hands and one best differentiation of the point count index between normal pair of hands and one involved in shooting is given in Table 3. A representative sample of the point count for involved in shooting is given in Table 3. A representative sample of the point count for normal hands and for those involvedin aa single firing isisgiven ininTables 4 4and 5. It is Tables and 5. It normal hands and for those involved in single firing given seen that a total point count higher than 5 indicates the presence of gunshot residue. By seen that a total point count higher 5 indicates the presence of gunshot residue. By
this method, a maximum success rate of 85 to 90 percent has been realized. In the this method, m a x i m u m success rate of 85 to 90 percent has been realized. In the
remaining cases, no differentiation can be made. There are probably many reasons for remaining cases, no differentiation can be made. There probably many reasons this, and among them are high occupational background values or aa lack of leakage this, and among them are high occupational background values or lack of leakage residues on a particular firing. residues on a particular firing. In calculating the point count, no assumption is made as to which is the firing hand. calculating the point count, no assumption is made as to which is the firing hand. It can be seen that if the wrong assumption is made, the point count is low, indicating can be seen that if the wrong assumption is made, the point count is low, indicating that the assumption is invalid or insignificant. The results are valid when either the right the assumption is invalid or insignificant. The results are valid when either the right or the left hand is used for firing. the hand used for firing.
Versus Handling A Gun Firing Versus Handing A Gun
has been reported 6 that firing a gun leaves residues on the back of the hand, It has been reported 6 that firing a gun leaves residues on the back of the hand, while merely handling aa recently fired weapon leaves the residue on the palm. The while merely handling recently fired weapon leaves the residue on the palm. The
KRISHNAN ON GUNSHOT RESIDUE DETECTION KRISHNAN ON GUNSHOT RESIDUE DETEOTION
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TABLE 3--Pointsgiven for various levels of trace element contents on the hand: hand: TABLE 3--Points given for various levels of trace element contents on the weapon--.38 revolver, ammunition--Dominion. weapon--. 38 revolver, ammunition--Dominion.
Element Element
Lead Lead
Amount, /ag
Amount on Firing H a n d / on Firing Hand. Amount on Other Hand Amount Hand
Points
2 1 1 0 4 3 0 2 1 1 0 4 3 3 0 2 1 1 0 4 3 0
85 /85 35 /35
35 35
2 1.5
3.5 1.5
/3.5 /1.5 1.5 1.5
t2 /1.5 1.5 1.5
Antimony
0.3 /0.3
0.1 /0.1
0.1 0.1
Barium
0.3 / 0.3
0.25 / 0.25
0.25 0.25
2.5 /2.5 1.5 /1.5
1.5 1.5
TABLE 4--Point count for normal hand blanks. for normal hand blanks. T A B L E 4----Point
Lead Lead Amount Ratioa Amount Ratio a
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2
Subject
1 1 2 3 4 5 6 7 7 8 8 9 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Antimony Amount Amount Ratio a Ratioa
0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0 1 1 0 1 1 2 1 1
Barium Barium Ratio a Amount Ratioa
Total
0 0 4 4 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 3 0 0 0 0 0 0 0 3 3 0 0 3 0 0 0 3 0 0 3 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
4 3 0 0 3 0 0 0 0 0 0 3 4 0 0 4 0 0 0 4 0 1 1 5 3
a Amount on firing h a n d / a m o u n t on the other hand. A m o u n t on firing hand/amount other
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TABLE 5--Point count ffor shots fired without prior cleaning one shot fired with a. 38 revolver S--Point count o r shots without prior one shot with a. 38 revolver and Dominion ammunition. Dominion ammunition.
1 1
Lead Lead Amount Ration Ratio a
Amount
1 1 1 1
Antimony Ratio a Ratioa
Barium Ratio 5 Amount Ratio a
0 0 0 0 2 0 0 0 1 1 0 0 2 2 2 2 2 1 1 1 0 0 3 3 0 0 0 0 3 3 3 4 0 0 4 3 0 0 3 0 0 0 0
12 7 8 2 14 12 16 16 12 13 13 3 3 6 10 15 8 9 13 11 11 7 3
2 3 4 5 6 7 8 9 10 10 11 11 12 12 13 13 14 15 16 16 17 17 18 18 19 19 20
2 2
2 2 3 1 1 1 1 2 1 1 1 1 1 1 1 1 2 2 1 1 1 1 1 1 1 1
4 4 3 0 4 3 4 4 4 0 3 3 4 3 0 4 4 4 4 0
1 1 2 1 1 0 1 1 2 0 2 2 2 2 2 2 2 2
0 4 3 4 3 3 0 0 0
0 3 0
3 3 3 0 0
a Amount on firing hand/amount on the other hand. Amount on firing hand/amount other hand.
experiments conducted in this work indicated that, while this may be generally true, the experiments conducted in this work indicated that, while this may be generally true, the
results are not consistent in all cases. The technique used in this work collects the results are not consistent in all cases. The technique used in this work collects the
samples from all areas of the hands together and, hence, it cannot determine the relative samples from all areas of the h a n d s together and, hence, it c a n n o t d e t e r m i n e the relative amounts on the palms and backs of the hands. However, aan interesting result is tthat in a m o u n t s on the palms a n d backs of h a n d s. However, n interesting result is h a t in the case of an actual firing, the point count on the firing h a n d is greater tthan 5, while the case of a n actual firing, the point count on the firing hand is greater h a n 5, while for the other hand it is usually below 5. If the gun has merely been hhandled in a random other h a n d it is usually below 5. If the gun has merely been a n d l e d in a r a n d o m manner, but not fired, the residues are usually left on bboth hands. In these instances, the m a n n e r, b u t not fired, residues are usually left on o t h hands. In these instances, the point count for both hands is above 5. count b o t h h a n d s is above 5.
Other Guns Guns
Preliminary experiments have been done to study the amount of residues deposited Preliminary experiments have been done to study the a m o u n t of residues deposited from guns other than. 38 caliber revolvers. These include. 22 caliber revolvers, pistols, from guns other t h a n. 38 caliber revolvers. These include. 22 caliber revolvers, pistols, and shotguns. Compared to the amounts of residue from. 38 caliber revolvers, the. 22 and shotguns. C o m p a r e d to the a m o u n t s residue from. 38 caliber revolvers, the. 22 caliber revolver, the. 22 caliber ssemiautomatic rifle, a n d the. 22 caliber Cooey single-shot caliber revolver, the. 22 caliber e m i a u t o m a t i c rifle, and the. 22 caliber Cooey single-shot rifle deposit less residues. The. 45 caliber semiautomatic pistol yields considerably more rifle deposit less residues. T h e. 45 caliber semiautomatic pistol yields considerably more residues, while the. 22 caliber semiautomatic pistol deposits o m p a r a b l e m o u n t s. The residues, while the. 22 caliber s e m i a u t o m a t i c pistol deposits ccomparableaamounts. T h e. 308 caliber semiautomatic rifle yields ccomparableamounts. FFurtherwork aandmore ddata. 308 caliber semiautomatic rifle yields o m p a r a b l e amounts. u r t h e r work n d more a t a are necessary to establish the method for use with other weapons. necessary to establish the m e t h o d for use with other weapons.
Trace Elements fTom Other Sources Trace Elements from Other Sources
Firearm discharge residues are present at a shooting scene a n d on the fired weapon F i r e a r m discharge residues are present at a shooting scene and on the fired weapon and spent cartridges. They are easily transferred by contact and, therefore, it is possible and spent cartridges. They are easily transferred by contact and, therefore, it is possible that touching the hands of a person who has recently fired a weapon, handling a fired that touching h a n d s of a person who has recently fired weapon, h a n d l i n g a fired
795
weapon, removing a fired cartridge, and similar acts could leave residues on a person s weapon, removing a fired cartridge, and similar acts could leave residues on a person s although himself has not fired a weapon. However, is found that these acts hand, although he himself has not fired a weapon. However, ititis found that these acts usually contaminate both hands, thereby giving point counts of greater than for each usually contaminate both hands, thereby giv.ng point counts of greater than 55for each hand.
Between Shooting Sample Effect of Time Lapsed Between Shooting and Sample Collection
The time which the residues remain on the hands after the shooting The length of time during which the residues remain on the hands after the shooting is an important factor. This obviously depends on what is done to the hands during the important factor. This obviously depends on what is done to the hands during the interval. If the residue is easily and quickly removed in normal hand usage, the value of the residue is easily and quickly removed in normal hand usage, the value the technique for application to cases in which the subject is examined some hours after to cases in which the subject is examined some hours after the technique the incident is limited. If the residue is relatively difficult to remove in the course of incident limited. the residue is relatively difficult to remove in the course of normal hand activity for several days, a different problem exists. A suspect could claim activity several days, exists. could claim the residue found his hand is result of firing several days previous to the that the residue found on his hand is aa result of firing several days previous to the
incident. The results of experiments to study this possibility show that the residue can The experiments to possibility show that the residue to 17 during normal activity, but can be quickly removed by vigorous remain for up to 17 hhduring normal activity, but can be quickly removed by vigorous scrubbing with soap and water. This is an encouraging and useful result. soap This an encouraging useful
Blind Tests
An attempt was made to test the criteria and hypothesis developed above in simulated test the criteria and hypothesis developed above in simulated situations similar to those encountered in actual criminal cases. Test shots were fired by to those criminal cases. were fired some members of a group and by others. samples were taken immediately after some members of a group and not by others. The samples were taken immediately after the firing in order to simulate suicide situations. In other similar tests, the samples were firing suicide situations. In other similar tests, the samples were
taken two hours later to simulate holdup situations. The actual identities of the taken two hours later to simulate holdup situations. The actual identities of the
individuals who had fired the guns were not known to the analyst and their identities individuals who had fired the guns were not known to the analyst and their identities were revealed only after the final reports were made. The results are given in Tables 6 were revealed only after the final reports were made. The results are given in Tables 6 7. These the concept method developed for deducing that and 7. These results indicate that the concept of the method developed for deducing that an individual has recently fired a gun is meaningful. Correct deductions were arrived at individual recently fired gun is meaningful. Correct deductions were arrived at in seven out of ten firings. No false positives were obtained; that is, in no case was a seven out firings. No false positives were obtained; that is, in no case was a occurred. firing indicated by the analysis when it had not, in fact, occurred. when it had order to test the method completely, gunshot residue collection kits were given to In order to test the method completely, gunshot residue collection kits were given to police officers. They conducted blind tests similar to the above series using mainly police officers. They conducted blind tests similar to the above series using mainly laboratory workers, collected the samples themselves, and sent them to the laboratory for workers, collected the samples themselves, and sent them to the laboratory for analysis. The results of the analysis are given in Table 8. The results were excellent analysis. The results of the analysis are given in Table 8. The results were excellent
TABLE 6--Results of blind tests to simulate suicide situations: weapon--.38 revolver, TABLE 6--Results o f tests to simulate suicide situations: weapon--.38 revolver, ammunition--Dominion. taken immediately after shooting. ammunition--Dominion. Samples taken immediately after shooting.
Point Count
Subject a Right Hand Left Hand Subject Left
Report Turned In
no evidence of gunshot evidence gunshot residue residue evidence of residue evidence residue no evidence of residue evidence residue no evidence of residue evidence residue evidence of residue on right evidence hand
Actual incident incident
5 5
8 3 3 4
5 S
7 7
fired one shot with right hand shot with right hand fired with both hands with hands fired one shot with right hand one right hand did not fire not fire fired one shot with right hand one shot with right hand
3 3 4 5
3 3
a Laboratory workers. Laboratory workers.
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TABLE 7--Results of blind tests to simulate holdup situations: weapon--. 38 revolver, TABLE 7--Results blind tests to simulate holdup situations: weapon--.38 revolver, ammunition--Dominion. Samples taken 2 h after the shooting. ammunition--Dominion. Samples taken h after the shooting.
Subject a Subject
Point Count Right Hand Left Hand Right Hand Left Hand
Report Turned In Report Turned
no evidence of gunshot residue evidence of residue on right evidence of residue on hand no evidence of residue no evidence of residue evidence of residue on right evidence of residue on hand
Actual Incident Actual fired one shot with right hand fired one shot with right hand
2 2 3 4 5
6 6 3 3 3 3 6 6
4 4
did not fire not did not fire fired one shot with right hand
a Laboratory workers. TABLE 8--Blind tests conducted by police officers: weapon--. 38 revolver, ammunition: Dominion. TABLE 8--Blind conducted by police officers: weapon--.38 revolver, ammunition: Dominion. Samples immediately after shooting. Samples taken immediately after shooting.
Point Co unt Count Subject a Right Hand L eft Hand Right Hand Left Hand Subjecta
Report Turned In Report Turned In
evidence of residue on right hand no evidence of residue no evidence evidence of residue on right residue hand slight evidence of residue on evidence
hand right hand
Actual Incident Actual fired one shot with right hand one with right
13 0 10 5 10
0 0 5 S
1 l
2 3 4
did not fire or handle gun handle
fired one shot by right hand fired one shot by right hand
removed and removed spent cartridge
fired using both hands using both fired one shot with right hand fired one
5 6 7 7
2 11 12
3 6
13 10 11
evidence of residue on right evidence of residue hand evidence of residue on left on left hand evidence of residue on both evidence of residue hands evidence of residue on right evidence of residue on hand evidence of residue on right evidence of residue on hand evidence of residue on right evidence of residue on
fired with right hand and refired with right hand and removed moved cartridges handled and removed cartridges handled and removed cartridges
from fired weapon, did not from fired weapon, did not
fire fired one shot with right hand with
0 0 0
did not fire or handle gun not fire handle gun
fired one shot with right hand with
hand hand
Laboratory workers Subjects 3 and 9, who are police officers. a Laboratory workers except for Subjects 3 and 9, who are police officers.
except for Subject 9. T h e results for Subject 9 a p p e a r to be a false positive, tthe only such e x c e p t for Subject 9. The results for Subject 9 appear to b e false positive, h e only such
one in all t h e tests c o n d u c t e d. Discussions have revealed a t the u b j e c t is a police one in all the tests conducted. Discussionshave revealed t hthatt h e ssubject is a police officer and regularly carries gun. Therefore, it p p e a r s h a t h e method may not always officer a n d regularly carries aa gun. T h e r e f o r e, it aappearstthat tthe m e t h o d m a y n o t always be applicable to people such as police officers w h o m a y ffrequentlyhhandle or fire g u n s. be a p p l i c a b l e p e o p l e s u c h as police officers who may r e q u e n t l y a n d l e or fire guns. When tthe ttechnique gives aappointccountggreatert h a n S5 for one hhand a n d lower tthan 5 W h e n h e e c h n i q u e gives o i n t o u n t r e a t e r than for one a n d and lower h a n 5
KRISHNAN ON GUNSHOT RESIDUE DETECTION ON GUNSHOT RESIDUE DETECTION
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for the other, then it it is clearly indicative that the subjectfired afired aIn instances the other, then is clearly indicative that the subject has has gun. gun. In instances where the counts both hands are greater than 5, other possibilities such as where the point counts for both hands are greater than 5, other possibilities such as contamination, firing with both hands, partial washing of the hands, and several others contamination, firing with both hands, partial washing of the hands, and several others
exist and these must be carefully considered. must be carefully considered.
It has been reported that the trace elements discussed in this work arise from the has been reported that the trace elements discussed in this work arise from the primer composition. Although this may well be true, no conclusive experimental primer composition. Although this may well be true, no conclusive experimental evidenceexists that these elements originate inin theirentirety from the primer. In our evidence exists that these elements originate their entirety from the primer. In our
opinion, it is possible that certain amounts of the trace elements arise from other parts it possible that certain amounts of the trace elements arise from other of the ammunition as well. The presence of leakage residues is decided by several the ammunition well. The presence of leakage residues is decided by several factors, among these the ammunition composition and the type of gun. Thus, when factors, among these the ammunition composition and the type of gun. Thus, when encountered with a case involving, for example, a. 22 caliber revolver with ammunition with case involving, for example. 22 caliber revolver with having no antimony or barium in the primer, it would still be necessary to perform having no antimony or barium in the primer, it would still be necessary perform test firings in order to decide that leakage residues would not be emanated from the gun firings to decide leakage residues would not be emanated from the gun and ammunition. ammunition.
Summary
A practical and effective method of detecting firearm discharge residues on hands is effective method of detecting firearm discharge residues on hands is reported. This involves the quantitative determination of lead by atomic absorption specinvolves the quantitative determination of lead by atomic absorption spectrophotometry and antimony and barium by neutron activation analysis. A procedure is and trophotometry and activation analysis. A procedure is developed in which a criterion is established for distinguishing between hands that have developed inwhich criterion is established distinguishing between hands that have
fired a weapon and those that may not have fired one. This is based on the absolute fired weapon and those that may not have fired one. This is based on the absolute
amounts of the trace elements and the ratios of these on one hand to the other. amounts of the trace elements and the ratios of these on one hand to the other. Collectionof voluminous background data isisnot required. The method has been Collection of voluminous background data not required. The method has been
successfullytested in twenty simulated case situations and is ready to be presented. in successfully tested in twenty simulated case situations and is ready to be presented.in court.
Acknowledgments Acknowledgments
The author wishes to acknowledge the excellent cooperation and help of the director, wishes to acknowledge the excellent cooperation and help of the D. M. Lucas, Mr. E. G. Clair, Mr. R. C. Nichol, and the members of the Firearms and Lucas, Mr. Clair, R. C. Nichol, and the members of the Firearms and
Chemistry Sections of the Centre of Forensic Sciences. Forensic
References References
1 Krishnan, S. S., Rapid Detection of Firearm Discharge Residues by Atomic Absorption /1 Krishnan, S. S., Rapid Detection of Firearm Discharge Residues by Atomic Absorption and Activation Analysis, Journal 1971, pp. 144Neutron Activation Analysis, Journal of Forensic Sciences, JFSCA, Vol. 16, 1971, pp. 144Sciences, JFSCA, 151. 2 Schlesinger, L., Lukens, H. R., Guinn, V. P., Hackleman, P., and Korts, R. F., 2 Schlesinger, H.H. L., Lukens, H. R., Guinn, V. P.,Hackleman, R.R. P.,and Korts, R. F., Report on Gunshot Residues Measured by Neutron Activation Analysis, Gulf General Special Report on Gunshot Residues Measured by Neutron Activation Analysis, Gulf General Atomic Inc. Report No. GA-9829, 1970. Report No. GA-9829, 1970. 3 Green, A. L. and Sauve, J. P., The Analysis of Gunshot Residue by Atomic Absorption 3 Green, A. and Sauve, J. P., The Analysis of Gunshot Residue by Atomic Absorption Atomic 93-95. Spectrophotometry, Atomic Absorption Newsletter, Vol. 11, 1972, pp. 93-95. Renshaw, G. D., Pounds, C. A., and Pearson, E. F., The Quantitative Estimation of Lead, 4 Renshaw, G. D., Pounds, C. A., and Pearson, E. F., The Quantitative Estimation of Lead, Antimony and Barium in Gunshot Residues by Non-Flame Atomic Absorption SpectrophotoBarium in Gunshot Residues by Non-Flame Atomic Absorption Spectrophotometry, Atomic Absorption Newsletter, Vol. 12, 1973, pp. 55-56. metry, Atomic Absorption Newsletter, Vol. 12, 1973, pp. 55-56. and Krishnan, S. S., Analysis Lead Shot--A Comparison of Analysis Using 5 Gillespie, K. A. and Krishnan, S. S., Analysis of of Lead Shot--A Comparison of Analysis Using Spectrophotometry Neutron Activation Analysis, Canadian Society of Atomic Absorption Spectrophotometry and Neutron Activation Analysis, Canadian Society of Forensic Forensic Science Journal, Vol. 2, 1969, pp. 95-103. Journal, Vol. 2, 1969, pp. 95-103. Guinn, V. P., private communication, 1972. 6 Guinn, V. P., private communication, 1972.
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Application of lead isotope analysis in shooting incident investigations Forensic neutron activation analysis of On the mechanism of gunshot residue particle.
Detection of gunshot residue by use of the scanning electron microscope. R S Nesbitt such as atomic absorption or ICP and is currently the most reliable method.
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