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The Detection of Spermatozoa in the Mouth
0Forensic Science Society
ORIGINAL PAPERS
1986
The Detection of Spermatozoa in the Mouth GM WILLOTT and MA CROSSE The Metropolitan Police Forensic Science Laboratory, 109 Lambeth Road, London, United Kingdom SE1 7LP
Abstract A survey of cases involving oral intercourse has been carried out to find whether semen is more likely to be detected on mouth swabs or in saliva samples. In a total of 61 cases, spermatozoa were found on only 10 of the mouth swabs but were present in 22 of the saliva samples. Spermatozoa were detected in the buccal cavity up to 13 hours after oral intercourse.* Key Words: Spermatozoa; Mouth; Swabs; Survival; Saliva. Journal of the Forensic Science Society 1986; 26: 125-128 Received 12 March 1985 Introduction Oral intercourse has been alleged in almost 20% of the sexual assault cases submitted to the Metropolitan Police Forensic Science Laboratory during the last year. Although exact details are not always available, most of the cases involve fellatio. In such cases, one or more mouth swabs should be taken by the police surgeon during the medical examination and sent to the laboratory to be tested for the presence of semen. Semen is usually identified by finding spermatozoa. During the course of the laboratory examination, there have been cases in which the saliva sample taken for the purpose of identifying the individual's blood group has been found to contain spermatozoa [I]. A survey has therefore been carried out to assess whether spermatozoa are more likely to be detected in saliva or on mouth swabs in cases in which fellatio has been alleged. In addition, the length of time the spermatozoa had persisted in the mouth has been recorded. Materials and methods Mouth swabs The swabs used during this survey were plain cotton wool swabs supplied by Medical Wire and Equipment Co. Ltd., Corsham, Wiltshire, UK (ref: MW 104). They were examined for spermatozoa as follows. * See author's comment at the end of this paper. 125
The whole swab was extracted in 1 ml distilled water and centrifuged at 1000 g for 2 minutes. The supernatant fluid, which can be used for other tests, was removed and the pellet was resuspended in a drop of water to provide a suitable concentration of material to be spotted onto a microscope slide. After being dried on a hot plate, and heat fixed in a Bunsen flame, the slide was stained with haematoxylin for 5-10 minutes, rinsed in water and counterstained with aqueous eosin for 1 minute. The eosin was washed off with water; the slide was then dried on a hot plate and the sample was mounted in XAM neutral white mounting medium.
Saliva The following procedure has been used for saliva samples. A sample of the saliva was placed in a centrifuge tube and diluted with 10 ml distilled water. The saliva was dispersed in the water with a disposable pipette and centrifuged for 10 minutes, and the supernatant fluid was removed. This procedure from dilution to removal of the supernatant fluid was repeated twice. Drops of the cell suspension were then placed onto a microscope slide and stained with haematoxylin and eosin as described previously.
Results Sixty-one cases have been examined where fellatio has been alleged and in which paired mouth swabs and saliva samples have been submitted to the laboratory. It is clear from Table 1 that spermatozoa have been found more often in saliva than on mouth swabs. In 7 of the 10 cases where spermatozoa were found on mouth swabs, they were also observed in the saliva. Thus, there were 3 cases where oral intercourse was demonstrated by finding spermatozoa on mouth swabs alone, whereas there were 15 cases where the offence was proved from the examination of the saliva alone.
TABLE 1 Paired saliva samples and mouth swabs showing how often spermatozoa were found on mouth swabs or in saliva alone
Spermatozoa present Spermatozoa absent
I n saliva only
In saliva and on mouth swabs
15
7
3
36
O n mouth swabs only
Toral in saliva
Total on mouth swabs
3
22(36%)
10(16%)
15
39(64%)
51(84%)
The length of time that spermatozoa have been found to persist after oral intercourse is shown in Figure 1. The longest time intervals recorded so far are 8 hours for mouth swabs and 13 hours for saliva samples. Twenty of the cases shown in Table 1 are not included in Figure 1 because the time intervals were not known. 126
10
.
I With
spermatozoa spermatozoa
L - 3 %Without
Hours after alleged offence
FIGURE 1 Occurrence of spermatozoa in (a) mouth swabs, and (b) saliva.
Discussion Detection of semen on mouth swabs and in saliva samples The comparison of results from saliva samples and mouth swabs has indicated that spermatozoa were found more often in the saliva. However, there were three cases in which semen was detected on the mouth swab and not in the corresponding saliva. Further investigation of these cases revealed the following details. In one case, the victim had washed out her mouth before the samples were taken. In the second, she had wiped out her mouth but the swab on which spermatozoa were found was taken from under the tongue. No spermatozoa were found on a swab from the gums in the same case. In the third case, a swab from the roof of the mouth bore spermatozoa whereas a swab from other areas of the mouth did not. The medical examination in these three cases was 2.5, 3 and 8 hours, respectively, after the offence. Persistence of spermatozoa in the mouth The results shown in Figure 1 indicate that spermatozoa can persist for several hours in the mouth, the longest time recorded being 13 hours. It is
therefore appropriate to take oral samples even if the offence occurred some time before the medical examination. Previously, the longest time after fellatio that spermatozoa have been detected in the mouth was also 13 hours [2]. Before that report, the longest time recorded was 6 hours from mouth swabs and 9 hours from a swab of the lips [I].
Author's comment Since this paper was submitted for publication, a saliva sample, taken 16 hours after the offence, has been found to contain spermatozoa. Acknowledgement We wish to thank Mr A Emes for the procedure for preparing saliva samples for examination and Mr M Paterson for his help in drawing the histograms.
References 1. Willott GM and Allard JE. Spermatozoa-their persistence after sexual intercourse. Forensic Science International 1982; 19: 135-154. 2. Tumosa CA. Persistence of sperm in the oral cavity. Crime Laboratory Digest 1984; 11: 16-17.
ORIGINAL PAPERS
1986
The Detection of Spermatozoa in the Mouth GM WILLOTT and MA CROSSE The Metropolitan Police Forensic Science Laboratory, 109 Lambeth Road, London, United Kingdom SE1 7LP
Abstract A survey of cases involving oral intercourse has been carried out to find whether semen is more likely to be detected on mouth swabs or in saliva samples. In a total of 61 cases, spermatozoa were found on only 10 of the mouth swabs but were present in 22 of the saliva samples. Spermatozoa were detected in the buccal cavity up to 13 hours after oral intercourse.* Key Words: Spermatozoa; Mouth; Swabs; Survival; Saliva. Journal of the Forensic Science Society 1986; 26: 125-128 Received 12 March 1985 Introduction Oral intercourse has been alleged in almost 20% of the sexual assault cases submitted to the Metropolitan Police Forensic Science Laboratory during the last year. Although exact details are not always available, most of the cases involve fellatio. In such cases, one or more mouth swabs should be taken by the police surgeon during the medical examination and sent to the laboratory to be tested for the presence of semen. Semen is usually identified by finding spermatozoa. During the course of the laboratory examination, there have been cases in which the saliva sample taken for the purpose of identifying the individual's blood group has been found to contain spermatozoa [I]. A survey has therefore been carried out to assess whether spermatozoa are more likely to be detected in saliva or on mouth swabs in cases in which fellatio has been alleged. In addition, the length of time the spermatozoa had persisted in the mouth has been recorded. Materials and methods Mouth swabs The swabs used during this survey were plain cotton wool swabs supplied by Medical Wire and Equipment Co. Ltd., Corsham, Wiltshire, UK (ref: MW 104). They were examined for spermatozoa as follows. * See author's comment at the end of this paper. 125
The whole swab was extracted in 1 ml distilled water and centrifuged at 1000 g for 2 minutes. The supernatant fluid, which can be used for other tests, was removed and the pellet was resuspended in a drop of water to provide a suitable concentration of material to be spotted onto a microscope slide. After being dried on a hot plate, and heat fixed in a Bunsen flame, the slide was stained with haematoxylin for 5-10 minutes, rinsed in water and counterstained with aqueous eosin for 1 minute. The eosin was washed off with water; the slide was then dried on a hot plate and the sample was mounted in XAM neutral white mounting medium.
Saliva The following procedure has been used for saliva samples. A sample of the saliva was placed in a centrifuge tube and diluted with 10 ml distilled water. The saliva was dispersed in the water with a disposable pipette and centrifuged for 10 minutes, and the supernatant fluid was removed. This procedure from dilution to removal of the supernatant fluid was repeated twice. Drops of the cell suspension were then placed onto a microscope slide and stained with haematoxylin and eosin as described previously.
Results Sixty-one cases have been examined where fellatio has been alleged and in which paired mouth swabs and saliva samples have been submitted to the laboratory. It is clear from Table 1 that spermatozoa have been found more often in saliva than on mouth swabs. In 7 of the 10 cases where spermatozoa were found on mouth swabs, they were also observed in the saliva. Thus, there were 3 cases where oral intercourse was demonstrated by finding spermatozoa on mouth swabs alone, whereas there were 15 cases where the offence was proved from the examination of the saliva alone.
TABLE 1 Paired saliva samples and mouth swabs showing how often spermatozoa were found on mouth swabs or in saliva alone
Spermatozoa present Spermatozoa absent
I n saliva only
In saliva and on mouth swabs
15
7
3
36
O n mouth swabs only
Toral in saliva
Total on mouth swabs
3
22(36%)
10(16%)
15
39(64%)
51(84%)
The length of time that spermatozoa have been found to persist after oral intercourse is shown in Figure 1. The longest time intervals recorded so far are 8 hours for mouth swabs and 13 hours for saliva samples. Twenty of the cases shown in Table 1 are not included in Figure 1 because the time intervals were not known. 126
10
.
I With
spermatozoa spermatozoa
L - 3 %Without
Hours after alleged offence
FIGURE 1 Occurrence of spermatozoa in (a) mouth swabs, and (b) saliva.
Discussion Detection of semen on mouth swabs and in saliva samples The comparison of results from saliva samples and mouth swabs has indicated that spermatozoa were found more often in the saliva. However, there were three cases in which semen was detected on the mouth swab and not in the corresponding saliva. Further investigation of these cases revealed the following details. In one case, the victim had washed out her mouth before the samples were taken. In the second, she had wiped out her mouth but the swab on which spermatozoa were found was taken from under the tongue. No spermatozoa were found on a swab from the gums in the same case. In the third case, a swab from the roof of the mouth bore spermatozoa whereas a swab from other areas of the mouth did not. The medical examination in these three cases was 2.5, 3 and 8 hours, respectively, after the offence. Persistence of spermatozoa in the mouth The results shown in Figure 1 indicate that spermatozoa can persist for several hours in the mouth, the longest time recorded being 13 hours. It is
therefore appropriate to take oral samples even if the offence occurred some time before the medical examination. Previously, the longest time after fellatio that spermatozoa have been detected in the mouth was also 13 hours [2]. Before that report, the longest time recorded was 6 hours from mouth swabs and 9 hours from a swab of the lips [I].
Author's comment Since this paper was submitted for publication, a saliva sample, taken 16 hours after the offence, has been found to contain spermatozoa. Acknowledgement We wish to thank Mr A Emes for the procedure for preparing saliva samples for examination and Mr M Paterson for his help in drawing the histograms.
References 1. Willott GM and Allard JE. Spermatozoa-their persistence after sexual intercourse. Forensic Science International 1982; 19: 135-154. 2. Tumosa CA. Persistence of sperm in the oral cavity. Crime Laboratory Digest 1984; 11: 16-17.