Impact of biological evidences on DNA profiling of sexual assault cases

Study group and design

This present study was carried out in the Biology & Serology Division of Regional Forensic Science Laboratory (RFSL), Northern Range, Dharamshala and DNA Division of State Forensic Science Laboratory, Junga, Himachal Pradesh, India. A total of 142 sexual assault cases (75 POCSO and 67 adults) registered under section 376, POCSO Act and other sections of Indian Penal Code (IPC) received from three districts of northern range of Himachal Pradesh during the year 2018-2019 were studied. 72 cases were received for forensic examination in 2018, out of which 39 were registered under POCSO Act whereas in 2019, 70 cases were received, out of which 36 were registered under POCSO Act.

Collection and analysis of data

The data was collected from the police forwarding letter, first information report (FIR), medico-legal report and results from the reports of Forensic Science Laboratory. Dried forensic exhibits and evidences were stored in exhibit storage chambers and liquid evidences such as blood, semen, saliva were stored at 4°C in refrigerator of forensic science laboratory. The variables such as time gap between the date of assault and medico-legal examination, menstruation status, barrier method of contraception used, status of survivor regarding bathing, changing and washing of clothing, undergarments, status of hymenal tears, type of assault, presence of seminal stains, anogenital and extra genital injuries, presence of spermatozoa in various samples such as pubic swab, vaginal swab and smear (lower, higher, external and internal), perineal swab, fornix swab (anterior and posterior), cervical swab and smear, periurethral swab, urethral swab, anal swab (inner and outer), vulval swab, rectal swab, introitus swab, buccal mucosa swab, hymenal swab, cervix slide, pericervical slide, posterior fornix smear slide, buccal mucosa slide, perineal swab slide, vaginal smear slide (internal and external), perineal smear slide, anal smear slide, cervical canal slide, pubic hair, seminal stain scrapping, fingernail clippings/scrapings, clothes of survivor and results of DNA profiling were entered in a self-designed proforma on Excel spreadsheet and statistically analysed.

Detection of spermatozoa

According to Locard’s principle of exchange ‘every contact leaves traces’. Likewise every act of sexual assault leaves behind some important trace evidences such as semen, blood, vaginal fluid, saliva, sweat, hair, fingernails or epithelial cells on the body and clothes of survivor, assailant and at scene of crime.14, 15 These biological evidences are of great importance in establishing the occurrence of crime. The presence of spermatozoa on survivor’s body, genital swabs and slides is considered as an absolute positive evidence of sexual assault. Other biological trace evidences can be found in case of any kind of struggle for self defense. Acid phosphatase test and microscopic examination were done in forensic evaluations to confirm the detection and presence of human semen and spermatozoa.16 In the present study, spermatozoa were detected and identified in 39 (27.46%) cases. The findings of our study were close to the study of Pal et al 17 and AlMadaniet al.18 who detected spermatozoa in 56(30.93%) and 25 (28.74%) cases.

Role of medico-legal examination and DNA results

When semen is detected on genital swabs, slides and clothes of survivor, then individualization of semen was done by obtaining a genetic profile through DNA technology. The developed profile was compared with the profiles of survivor and suspect. On the basis of genetic profiles, the suspect was included or excluded as a possible assailant of crime. In our study, an inclusion of assailant in sexual assault was reported in 29 (20.42%) cases and exclusion in 12 (8.45%) cases. In 103 (72.54%) cases, spermatozoa were not detected on clothes, genital swabs and slides of survivor so, the DNA profiling could not be done. Spermatozoa may not be detected in cases of fabrication of facts and false allegations by the survivors against the perpetrator or due to the loss and degradation of samples due to post assault activities like vaginal drainage, urinating, washing, bathing, changing clothes, douching of genitals and use of condom during the act and increasing intervals between the assault and medico-legal examination.These post assault activities by the survivor affect the quality and quantity of DNA. The reasons for delay in medico-legal examination may be non-disclosure of incident due to fear of reprisal of perpetrator, fear of shame, guilt, blemish on the character and reputation. The biological evidences got lost or degraded and there are chances of growth of microorganisms such as bacteria and fungi which breaks down the sperm and yields negative results.19, 20, 21

In many cases, it was observed that the survivors due to lack of knowledge had taken bath and changed clothes prior to medico-legal examination which resulted in loss or elimination of the important biological evidences. Among 142 cases of sexual assaults, 18 (12.68%) were examined on the same day of the assault. Our findings were similar to the study of Arifet al.22 who reported the same day examination in 18 (12.1%) cases. The results of present study were close to the findings of Pal et al,17 Sharaf El. Din23 and Pal et al24 who reported same day examination in 27 (14.91%), 12 (9.2%) and 3 (8.55%) cases respectively. In our study, 19 (13.38%) survivors underwent for medico-legal examination on second day, 18 (12.68%) within a week and 17 (11.97%) within 8 days to one month and 11 (7.75%) after one month. Our study was consistent with the study of Tamuli et al.6 who also reported medico-legal examination after one month of the assault in 28 (7.33%) cases. This shows that the maximum number of survivors underwent medico-legal examination on the second day of assault.

Status of survivor and spermatozoa on clothes

In the present study, 29 (20.42%) survivors had taken bath and washed clothes, 23 (16.20%) had taken bath and 22 (15.49%) had neither taken bath nor washed clothes, 11 (7.75%) had taken bath, changed clothes but did not wash clothes, 3 (2.11%) had taken bath but did not wash clothes, 1 (0.7%) had not taken bath, changed clothes but did not wash clothes and 1 (0.7%) had changed clothes but not taken bath before medico-legal examination and tested negative for the presence of semen/spermatozoa.

Only 39 cases were tested positive for spermatozoa, out of which 12 (8.45%) survivors had neither taken bath nor washed clothes, 8 (5.63%) had taken bath, changed clothes but did not wash clothes and 3 (2.11%) had taken bath and washed clothes, 4 (2.82%) had taken bath but did not wash clothes, 2 (1.41%) had taken bath and 1 (0.7%) had changed clothes but not taken bath before medico-legal examination. The results of our study were in contrast to the results of Arif et al.22 who reported that 122 (82.4%) survivors had changed clothes, 26 (17.57%) had changed clothes but did not wash and handed over the clothes worn at the time of assault. In the present study, dried secretions were found on clothing, bed sheets and bag of survivor in 34 (23.94%) cases. Our study was consistent with the study of Lavelle and Kellogg25, 26 who reported that dried secretions on clothing remain quite stable, so semen can be detected after a long time. The stains present on the associated evidences such as clothing and bedding will not be affected if they are kept in dry environment.20 Spermatozoa can be detected on washed clothes but the retention of sperm on clothes depends on the type of fabric, amount of ejaculation, type of detergent used, laundering temperature and time of washing of clothes which affects the presence of spermatozoa.27, 28, 29

Barrier methods of contraception used

Nowadays, rapists have been increasingly using some barrier methods of contraception during the sexual intercourse to avoid pregnancy and sexually transmitted diseases due to awareness of sex education through internet, electronic and print media. Condom is the most commonly used barrier method. The use of any barrier method of contraception may result in absence of seminal fluid on the body and clothing of survivor.^33-35Sexual dysfunction, vasectomized, oligospermic or azoospermic and even potent assailants with no ejaculation during the act could lead to absence of seminal fluid as semen without sperm cells may generate no DNA profile or a partial profile which is less informative. In such cases, other biological evidences like fingernail scrapings, epithelial cells, saliva, etc. play a major role. Fingernail scrapings and clippings can be a good source of foreign DNA, if the survivor has struggled with the perpetrator during the assault as blood, semen, saliva and epithelial cells of skin may be present on fingernails. Saliva is ample source of DNA as genetic profile of suspect can be generated from mucosal epithelial cells of the mouth using STR or Y-STR typing from saliva on genitals and other body parts of survivor where the suspect had kissed, licked or bitten during the assault. 20, 30 Our study reported that the assailant used condom during sexual assault in 7 (4.93%) cases. The results of our study contradicts with the study of O’Neol et al., 31 Davis et al.32 and Cerdes et al. 33 who mentioned that 112 (13.32%), 10 (29.4%), 190 (12%) assailants used condom during the assault.

Link between menstruation, semen and spermatozoa

Earlier, it was assumed that spermatozoa and seminal secretions might outflow during menstruation from the vagina of survivor thus decreasing the probability of finding semen in genital swabs and slides. But, the studies showed that menstruation did not affect the probability of finding semen in vagina and did not hamperthe results of DNA profiling.³⁸In our study, 10 (7.04%) survivors were menstruating at the time of assault and semen and spermatozoa were detected in 6 (4.22%) cases. The results of our study were in contrast to the results of Cerdaset al.³⁸conducted study on the 170 survivors who were menstruating at the time of assault and reported detection of spermatozoa in 101 (59.41%) cases. Cerdas et al. 34 mentioned that semen was detected in 149 (55%) and spermatozoa were detected in 90 (33%) samples. 33 2 (1.41%) survivors were pregnant and assailants were found to be biological father of the offspring. The results were in line with the study of Arif et al. 22 who reported pregnancy in 2 (1.3%) cases after the assault. The results of our study were close to the results of Pal et al. 24 who mentioned that 1 (2.85%) survivor was pregnant after the sexual assault.

Type of assault and status of hymeneal tears

The results of our study demonstrated that vaginal penetration was the most common pattern of crime in 115 (80.99%) cases. The results of our study were in line with the study of Kauret al.³⁹ and Adegoke and Adefolau 35 who reported vaginal penetration in 76 (76%) and 394 (73.78%) cases.Earlier hymen was considered as a sign of virginity and Two Finger Test or Per Vaginal (PV) examination was conducted to determine whether the survivor is habitual of having sex or not, but now this practice is banned as this violates right to privacy and hymen could also be ruptured during some intense activities like cycling, swimming, horse riding and use of menstrual cups and tampons during menstruation. The present study reported that hymen was ruptured in 56 (39.44%) cases and intact in 9 (6.34%) cases. The result of our study was close to the results of Pal et al.,17 AlMadani et al.18 and Abdellah and Ali36 who reported old healed tags in 40 (22.09%), 12 (29.3%) and 6 (13.04%) cases respectively. Our study was in agreement with the study of Tamuli et al.6 who reported intact hymen in 25 (6.54%) cases. The results of our study were close to the results of Pal et al.,17 Arif et al.,22 and Pal et al.24 who reported intact hymen in 22 (12.15%), 5 (3.3%), 4 (11.42%) cases. The hymenal tags or tearsdo not prove that vaginal penetration has occurred or not buttenderness, bruise, redness, perforation or tear around the vulva gives the indication regarding penetration.

Anogenital and extragenital injuries

Any kind of sexual contact without consent of the survivor may lead to injuries on the body. The injuries are caused due to struggle and self-defense by the survivor during the assault. During the assault, skin cells or hair may get deposited on the survivor. Even DNA profile can be generated from touch or other skin contact which have sufficient amount of DNA.37 Injuries on genitals, breasts, thighs and scratches on the back are commonly observed in sexual assault cases. In our study, the most common type of injuries found on the body of survivors were scratch marks over cheeks, thighs, contusion over thigh, abrasion on knee, left leg, vaginal wall, neck, front part of skull, posterior part of introitus and multiple abrasions, laceration/tear on lower part of vagina, multiple bruise on body, right thigh, fourchette, thigh, vulva, left breast, tear on sides of urethral opening on labia majora,rashes on vaginal wall, cut genetalia,reddish erythema on genitalia, bleeding on vaginal introitus opening. In 114 (80.28%) cases, no injury was found on the body of the survivor whereas anogenital and extra genital injuries were observed in 20 (14.08%) cases. Abrasion and bruises were the most common injuries found in 7 (4.93%) and 6 (4.23%) cases respectively. The results of our study were in contrast to the results of Pal et al.,24 Sherif et al.38 and Arif et al.22 who reportedanogenital and extragenital injuries in 11 (31.43%), 77 (33.62%) and 16 (10.8%) cases respectively. The presence of injuries showed that struggle has occurred between assailant and survivor during the forcible act of sexual assault. No injury on the body indicated that the survivor might be known to the assailant and due to acquaintance no resistance was shown by the survivor during the assault. In some cases, injuries got healed and could not be observed on the body due to delay in reporting the case to investigation agencies and medico-legal examination.

Discharge of semen

The presence of seminal stains on clothes and body of survivor do not directly prove the fact that any type of penetration has occurred or not, as the seminal stains can be present as a result of masturbation, any sexual perversions or discharge/spillage of semen by the assailant on the body parts of survivor. In our study, the dried seminal secretions were detected on both legs in 1 (0.7%) case and resulted in inclusion of assailant though dried stains on the skin have a limited amount of DNA.39 In the present study, 2 (1.41%) survivors narrated that assailant had kissed, touched, inserted an object and finger in genitals of survivor. In these cases, semen was detected on bed sheet, plastic sack, and salwar and DNA profile generated from these samples matched with the DNA profiles of assailant. This clearly suggests that the survivor’s statement providing information regarding the assault must be taken into consideration which can streamline the overall DNA analysis of the samples.