Investigation of crime with scientific and forensic vigour ensures transparency in evidence collection abiding by the oftquoted aphorism “Not only must justice be done; it must be seen to be done”. Both victim and accused are entitled to fair criminal proceedings with scientific investigation braced by forensic corroboration. Transparency in evidence processing builds faith in criminal justice apparatus. “Locard’s Exchange Principle”, the citadel for forensic sciences, says that when any person comes in contact with any object or any other person, a cross-transfer of physical evidence does occur. Admissibility of expert opinion is conditioned upon the inviolability of forensic sample which necessitates infallible procedural management to avoid tampering, manipulation and mishandling of samples. The procedural protocol must invoke evidence dynamics to annul scope of any influence to modify, obscure, relocate or obliterate physical evidence, regardless of bona fide or malicious intent.
Rape is a global challenge for public safety and protection of women and children. Sexual offences suffer from under-reporting and poor rate of conviction for want of credible evidence. Forensic corroboration of the sole testimony of the prosecutrix in sex crime becomes significant since these crimes occur in isolation, practically eliminating possibility of finding ocular witness. Since 1986, DNA has emerged as a potent evidentiary tool for corroboration of sole testimony of the prosecutrix. Matching of DNA profiles of biological contents exchanged between the prosecutrix and the accused has credible probative value. Touch DNA technology, especially Polymerase Chain Reaction (PCR), adds value especially when biological content is in traces. In forensic world, selection, collection, packaging, labelling, storage, preservation, transport and maintenance of chain of custody are vital steps for handling physical samples with utmost care and expertise aiming to avoid risk of contamination, destruction, loss or potential fiddle.
Serving Member of Indian Police Service from Uttar Pradesh and currently on deputation to the Government of India. Also pursuing research activities at Gujarat Forensic Sciences University (GFSU), Gandhinagar 382 007, India. Email: firstname.lastname@example.org (Corresponding Author)
This article is primarily intended to emphasise upon the importance of maintaining sanctity of forensic samples by timely conducting forensic medical examination (FME) of individuals or relevant spots to maintain sanctity and reliability of samples. Proposed standard operating procedures (SoP) would be a beacon of light for foot soldiers of law enforcement agencies to handle forensic samples without any legal or scientific procedural lapses. It further aspires to homogenise forensic intervention to improve competence of medicolegal experts for conducting FME; and assist courts to undertake comprehensive procedural evaluation of expert opinion in order to rebuild faith of common mass in judicial processes.
Police in India recommended prosecution in 96% cases of sexual offences in 2016 but secured conviction in only 25% cases. The pendency for trial of these cases is nearly 88%. The grim scenario of low rate of conviction coupled with delayed trial can be addressed by improving quality of investigation especially adducing corroboration by forensic evidence. Hostility of the prosecutrix due to various factors including acquaintance and proximity of the accused with rape survivor is a prominent reason for acquittal, which may be aptly addressed by forensic and medicolegal corroboration. Forensic tools would further brace prosecution story by cross-examination of a hostile witness in courtroom, in order to secure conviction. However, conducting scientific investigation needs skilled manpower trained in forensics and legal procedures supported by standard protocol for management of forensic footprints.
Synthesis of this protocol derives its focus from recent empirical study conducted to investigate role of DNA in administering justice in sexual assault cases in the State of Uttar Pradesh in India which has a population of approximately 200 million. The incidents of sexual violence in India are exceeding threshold level when compared to global scenario, emphasising for academic enquiry. A total of 998 investigating officers, 310 supervisory police officers and 350 Public Prosecutors responded during this empirical study through interview guides and questionnaires. 114 stakeholders as key informants such as forensic scientists, medicolegal experts, attorneys and Judges were interviewed for qualitative feedback. Specific case studies of rape incidents were also carried out to learn the status of DNA as evidence.
The study revealed that first responders to crime scene are not adequately trained in handling forensic samples and standard protocols are missing, consequently, investigators used DNA evidence only in 5% cases. On an average, investigators train only for around three days in their entire career on DNA evidence still 25% of them believe that they have sufficient skills for conducting scientific investigation. This mindset probably restricts them from learning and upgrading their investigative proficiency.
FORENSIC SAMPLES: NATURE AND SIGNIFICANCE
Forensic evidence may be traced and collected from various sources such as victim, accused or the environment. Physical samples after forensic analysis may furnish credible information used as secondary evidence helping in pursuit of truth. Forensic evidence validates fairness in investigation by reconstruction of crime scene, corroboration of oral statements and facts, identification of unknown victims or perpetrators with greater precision in blind cases. DNA evidence since inception has proved to be a panacea for correctional justice to secondary victimisation due to false accusation and wrongful conviction.
Indeed transforming forensic sample into admissible piece of evidence is an art requiring strict procedural regime including protection of crime scene from unwanted incursions. Mainly two types of physical evidence, either having non-biological origin such as fingerprint or footprint, shoe impression, tyre mark, soil, gunshot residue, cigarette butts, bottle, cans, glass, note, etc., or evidence of biological origin such as blood, semen, vaginal fluid, saliva, sweat, condom content, nail clips, bite marks, scrotal swab, etc. may be collected. Pollen grains, wood and plants may also have vital forensic links. Biological samples are potential source for DNA.
Nomenclature of forensic samples
Forensic sample collected from scene of crime or other source for matching is referred as Unknown/Questioned Sample. Standard/Reference Sample is collected from a known source of origin (like victim, accused, and other verifiable sources), mainly used for identification of unknown samples and accreditation of procedures. Controlled/blank sample has known source of origin used for comparative analysis for the purpose of inclusion or exclusion.
Consent for collecting DNA sample
Subject’s consent to collect DNA sample constitutes cornerstone of the right to privacy, protected by constitution in most of the jurisdictions. DNA discloses a catena of personal genetic information, hence prior consent of subject becomes overarching. Section 53-A of the Criminal Procedure Code, 1973 of India enables medicolegal expert to collect DNA sample of an accused of rape on advice of police officer. However, to collect biological sample and for conducting medicolegal examination of rape survivor, informed consent is mandatory. In the interest of justice, courts are provided with overreaching powers for balancing competing interests of individual and community in obtaining biological sample provided procedure of sample extraction is non-invasive in nature. However, issue of consent becomes more prominent in the light of the recent judgment of K.S. Puttaswamy v. Union of India, whereby the Supreme Court of India has recognised privacy as fundamental right, an integral part of right to life with dignity under Part III of the Indian Constitution.
Scope of forensic samples in rape incidents
In sexual violence, the history of incident helps a forensic examiner to locate and to collect samples of forensic significance. During sexual assault, semen, blood, saliva and hair may get exchanged between perpetrator and victim and may also be traceable on articles in contact. During physical examination, Wood’s lamp and Polilight help to detect stains of biological content.,  Video and photography of crime scene help to preserve the location of evidence.
Brief forensic importance of semen, blood and saliva is discussed below:
Semen.—Transfer of semen from male perpetrator to victim is a potent forensic marker. Semen is highly fluorescent under UV light and Wood’s lamp helps to detect semen stains. Indeed semen contains spermatozoa suspended in the seminal fluid. The chance of getting spermatozoa in oral, anorectal and vaginal cavities diminishes after 6, 24 and 72 hours respectively after sexual contact. In pre-pubertal girls, half-life of spermatozoa is comparatively shorter due to absence of cervical mucus. In post-pubertal girls, sperms may be motile in vaginal secretion for 6 to 12 hrs and in the cervix may be traced as long as 5 days. The dried stains of seminal or other body fluids on clothes or hard surface are relatively stable and may be detected even after one year. The motility of spermatozoa depends on several factors such as perpetrator may be azoospermic or vasectomised, hence, semen smear analysis under optical microscope may provide deceptive results because spermatozoa may be absent. Prostate-specific Antigen (PAS) is considered most sensitive marker for semen detection including azoospermic samples in addition to DNA analysis.
Blood.—Forensic serology mainly serum antigen and ABO group analysis traditionally provides clues for human identification. Blood being potent source of DNA, preferred as controlled sample for DNA forensics but it must be avoided subject has recent history of blood transfusion or bone marrow transplant. Blood stains on body, clothes and articles must be collected for DNA source. Blood or tissues from aborted foetus or pregnant dead victim may be potential source for DNA match.
Saliva.—In sexual assault cases, saliva provides vital forensic clue since perpetrator commonly kisses, sucks or bites the victim and oral fluid may prevail on the victim’s skin especially on her breast, neck, face, throat, abdomen, groin, etc. In case perpetrator intensively kisses the victim, DNA may be recovered up to one hour from buccal cavity of victim provided FME is accomplished soon and victim has not wash her mouth for hygiene. Butts of cigarettes, can/bottle of beverages, glass, etc. are also potential sources for this purpose. Phadebas test detects ?-amylase activity to identify saliva. Saliva contains epithelial cells to conduct DNA analysis.
Stability factors for DNA sample
DNA is relatively stable genetic molecule found in the nucleus of body cell. Various factors like time, chemical contact (washing of linen by soaps or detergents), external conditions (temperature, humidity, microbes) may adversely affect the stability of DNA. If FME is conducted within 72 hours of rape incident, chances of yielding credible forensic results are higher. Possibility to collect foreign DNA from different parts of body is contingent with time span as given below:
- DNA from vagina/cervix may ideally collect within three days but up to seven days under certain circumstances.
- DNA from anus — up to three days.
- DNA from penis — vaginal epithelial cells of victim may be recovered on glance penis within 12 hours.
- Fingernail scrapings — two days.
- Buccal cavity (saliva and mouth swabs) — two days.
- DNA from skin to skin contact (e.g. bruises or kissing) may be detected up to two days but up to seven days provided the subject has not showered.
- Lubricant from a condom — up to thirty hours.
These life spans are only indicative since factors like quantum of transfer of biological content may vary from case to case. Further, washing, bathing, urination, brushing, etc. may also impinge on finding trace DNA.
Advice to rape survivor before forensic medical examination (FME)
The rape survivor must persistently be provided psychological support by domain experts. FME must be conducted at the earliest to avoid obliteration of forensic evidence. The victim of sexual violence may be advised to refrain from following activities, as far as possible, before undergoing FME:
- Mouth wash or brush teeth, shower or cleaning any body part.
- Change, wash or destroy clothes, if already done, then preserve clothing worn at time of incident.
- Cutting or combing paint (sticky) hair.
- Cutting or cleaning fingernails.
- Drink, eat, chew or smoke.
- Urinate, defecate or vomit, if unavoidable, then collect in clean container with lid.
- Sport or athlete activities.
SOURCES OF DNA SAMPLES IN RAPE CASES
The medicolegal experts conduct detailed inspection of the bodies of the victim and the accused of sexual assaults for recording injuries and other vital information necessary for medicolegal report (MLR) and also conduct FME for collection of forensic samples from bodies and clothes of victim and the accused. Forensic experts collect relevant artifacts having forensic significance from crime scene.
The sources for DNA sample collection are as under:
Victim.—Vaginal swab, anal swab, buccal swab, breast swab, bite marks, pubic hair combing, saliva or semen stains, clothes especially undergarments to search for biological content for DNA analysis. Fingernail clips beneath hyponychium provide valuable evidence including hair, body fluids, fibres, vegetation, etc.
Accused.—Penal swab, buccal swab, bite marks, saliva or blood stains, fingernail clips, scrotal scrap, pubic hair combing, clothes.
Crime scene (place of occurrence).—Variety of biological tissues like plucked hair, stains of blood or semen, linen, fingerprints, etc. may be collected from condoms, sunglasses or eyeglasses, mobile or any other electronic device, bottles, cans, glass, cigarette butts, toothpick, chewed gum, food items, keys, vehicles, etc. Menstrual products, tampons, condoms from garbage may provide DNA content, however, vomit residue around toilet rim may be analysed for drug facilitated sexual violence. A clear fingerprint may be a potent source for touch DNA analysis.
Place other than crime scene.—Articles such as clothes of the victim or accused, weapon, mobile phone, wallet, etc. recovered from any other place on advice of the accused/suspect (recovery under Section 27 of the Indian Evidence Act, 1872) or witness may provide credible forensic evidence.
DNA KIT FOR EVIDENCE COLLECTION
Challenges of contamination and procedural inviolability of DNA sample may be addressed by using DNA kits having specialised items for forensic sampling. DNA kit must contain the following items:
- Instructions for the user
- Forms for documentation
- Bags and sheets for large sample collection
- Sterile sample containers
- Latex or nitrile disposable gloves and other Personal Protective Equipment (PPE) including eye protection, paper mask that covers nose and mouth, hair net, white paper body suit, sleeve protectors, shoe covers
- Blood collection devices including syringes and needles
- Tubes, vials, vacutainers for blood samples
- Swabs (sterile) of different size, shape and design to use for sample collection. Synthetic swabs made up of flocked nylon are preferred over cotton swabs.
- Wooden or plastic containers for collection of fluids from lips, cheeks, vagina, anus, thighs, buttock, etc.
- Swab boxes or other suitable container for packaging of swabs
- Disposable razor blade or scalpel
- Distilled water
- Bleach sterilisation solution (1:10), prepare fresh when needed
- Alcohol pads for cleaning
- Envelopes or bindle paper
- Paper wrapping and paper bags
- Evidence tape
- Biohazard labels
- Lac (sealing wax) sticks for sealing
SAFE Kit is a customised version of DNA kit to assist in collection and safe preservation of forensic evidence gathered from prosecutrix, accused/suspects and the crime spot of sexual assaults. In addition to items in DNA kit, SAFE kit generally contains the following additional items:
- Nail pick for scraping debris from beneath the fingernail hyponychium
- Comb used to collect hair and fibres from the victim’s body
- Ethylene diamine tetra acetic acid (EDTA), sodium fluoride
- Self-sealing envelopes for preserving the victim’s clothes, blood samples, pubic hair and head hair
- Clear glass slides
- White sheets to collect physical evidence stripped from the body
- Clean clothing, shower hygiene items for post-examination use by the survivors.
Other items for forensic/medical examination may include:
- Colposcope (to examine cervix, vagina and vulva)
- Vaginal speculums
- Camera (35mm, digital with colour printer)
- Magnifying glass
- Wood’s lamp or a torch
- Surgilube (lubricating agent)
- Post-It Notes to collect trace evidence
- Toluidine blue dye
- Urine Pregnancy Test Kit
- Patient gown, cover sheet, blanket, pillow
- Drying rack for wet swabs and clothing
COLLECTION OF BIOLOGICAL SAMPLES
Preserving samples from contamination and degradation is crucial precaution at any crime scene. Biological evidence may suffer from cross-contamination due to unprotected exposure to investigators, visitors or due to interface between biological specimens. In forensics, collection procedure may depend upon situation, location other than the nature of a sample. In sexual offences, tracing a biological sample is very critical, and alternate light source may be useful. The location of each stain found at crime scene must be duly documented (video-record and photograph). Priority must be given to collect biological material and trace evidence of fragile nature. It is preferable to submit the entire item, but if it is very large in size, then after photograph, relevant part of forensic worth must be collected for sampling.
Probable circumstances for collection of biological evidence are listed below:
Wet stain on absorbent surface.—A sterile dry cotton swab must be used for wet stain. Alternately, area of surface having wet stain must be cut by a clean and sterilised razor and for control sample adjacent area of surface (substrate sample) must be preserved.
Wet stain on non-absorbent surface.—One or more clean sterile swabs (or sterile gauze for larger stains) to soak up the stain must be used. Concentrate the stain on one portion of the tip of the swab (wooden or plastic swab stick), moisten the swab with distilled water and rub an area of the surface in an unstained region near the stain. Control sample must also be collected for the purpose of matching.
Dry stain on absorbent surface.—Cut the stained area and pack in a clean and dry white paper and collect a portion of unstained area as a control sample.
Dry stain on non-absorbent surface.—It is preferred to submit the entire item, if possible. In case not possible, then use a new or clean scalpel blade to scrape the stains from the surface on a clean white paper and fold properly for wrapping.
Sample from a smear.—A slightly dampened (with distilled water) sterile cotton swab must be used. In case of small stains, rubbing must be avoided and swab over the surface of entire stain; instead, apply constant pressure on the tip of the swab against the stain. Also collect a control sample by swabbing unstained adjacent surface areas with a new sterile swab moistened with a drop of distilled water. Allow the swabs to air dry and then package and label both swabs separately in envelopes or bindle paper.
Saliva and bite marks.—The interior and exterior areas of a bite mark should be swabbed with separate sterile swabs slightly moistened with distilled water and both swabs should be labelled accordingly. A clean sterile swab must be use to absorb wet saliva or mucous. The swabs must be dried in air before packaging them in separate envelopes followed by proper labelling.
Hair and fibres.—Three methods for collection of these trace evidence may be used:
(i) Visual collection.—In case hair and fibres are seen with naked eye on a surface, with the help of clean forceps and trace paper, the sample may be collected on to a clean piece of paper that must be folded and packaged in a paper envelope.
(ii) Tape lifting.—Trace tapes may be used to the location of probable area for collection of trace hair and fibres. The tapes carrying samples must be packaged in separate envelopes.
(iii) Vacuuming.—The area where the targeted samples are located must be vacuumed and evidence will be collected from filtered trap attached to the vacuum. These samples must be packaged in a clean trace paper. Vacuuming is the least desirable collection method because there is a risk of cross-contamination, if the equipment is not properly cleaned between each use.
Cigarette butts.—The butts must be handled after wearing gloves and never with bare fingers. The cigarette butts must be air dried before packaging. Cigarette ashes have no evidentiary DNA, but it may provide other forensic inputs like narcotics.
Underneath fingernail.—A damp and small thin tip swab must be used which may reach under the fingernails.
Sexual assault on bed or car.—In case, sexual assault happened on a bed or car, top surface of bed linen or seat fabric should be collected, especially the portion holding any stain, fibres and hair. An alternate light source may be used to locate hidden stains on bed linens or clothes invisible to naked eye. If wet stains are visible, a permanent marker must be used to discretely mark the location of wet stain and duly photographed. In case towel or tissue is used by the suspect and/or victim to clean up after the assault, it must be collected for getting trace evidence.
Controlled sample.—Biological samples like buccal swab, hair or blood is collected from the victim, accused/suspects and other related persons (acquainted with crime scene) for the purpose of inclusion or exclusion. In case of blood transfusion or bone marrow transplantation done to the subject, collecting blood for controlled sample is not preferable. In case of hair, at least seven hair with roots intact should be pulled out. In case of oral-genital contact or deep kissing by perpetrator, collecting buccal swab of the victim must be avoided for known sample since it may be contaminated by perpetrator’s DNA. In such circumstances, root intact hair or buccal swab are preferred.
Precautions during sample collection.—Forensic team must use disposable mask, powder free glove, gown, etc. and avoid talking, sneezing, coughing, eating-drinking, smoking to prevent contamination of samples. New gloves must be used while handling each artefact. Microbial contamination may be avoided by collecting samples under aseptic conditions. Double-tipped swabs must be avoided. For preventing sample loss, one swab for each item of evidence must be preferred because more swabs may reduce concentration. If any stain is cut from large clothes, new razor or blade must be used. Tape lifter should never be used to collect dry stains.
PACKAGING, LABELLING/TAGGING AND SHORT-TERM STORAGE
The sample must be properly dried up before packaging. If drying is not possible, samples (like tampons with blood, condom content, etc.) may be frozen. During packaging of biological material, due precaution depending on nature of evidence must be observed to prevent contamination, loss and degradation. Plastic wrappers, bags or containers should be avoided and self-sealing paper packages, foldable racks or bags must be preferred for sample packaging or storage. Wet or moist body fluids should not be stored in plastic bags for long time to avoid bacterial growth and contamination resulting into DNA degradation. The sample, especially clothes having biological fluids, stains or swabs collected from the subject must be properly dried in air before packaging. If blood or any other body fluid is soaked on a linen or garment, it should be wrapped with a sheet of clean white paper to protect stain patterns and prevent from possible cross-contamination, and inadvertent transfer of stains to unstained portions of the linen. A bindle may be used for packaging hair, fibres and leaves. All evidence should be packaged and sealed individually. Before sealing the package, the examiner/IO should put request form together with sample inside the kit. Packages should not be stapled and must be signed across the seal in order to detect possible tempering.
Labels list specifies the details from whom and where from the evidence was collected and may also include biohazard information. After proper labeling by biohazard designation, each sample must have a label/tag (ideally a bar coding/RFID) having following information:
- Case reference: FIR No., police station, district, State, etc.
- Item number.
- Sample type
- Location of recovery
- Date and time of recovery
- Investigator’s initial with name and date
The inventory of all labelled samples duly signed by two independent witnesses must be prepared and each sample must be photographed for maintaining chain of evidence. DNA may be degraded by adverse environmental factors such as heat, sunlight, bacteria and mould, hence, due precaution is warranted for safe preservation of perishable samples. During transport from scene of crime, samples must be stored in cool and dry environment and trunk of a police car should be avoided to carry the packaged evidence since it may get heated. A secured and well-equipped temporary storage facility is necessary to prevent degradation or contamination of biological samples. Direct sunlight and warm conditions may fasten DNA degradation. Ideally DNA samples must be stored in a refrigerator at 4°C or a freezer at -20°C to reduce DNA degradation or microbial growth.
SECURING “CHAIN OF CUSTODY” (COC) AND SAFE TRANSPORTATION OF SAMPLES
Authenticity of a sample is the hallmark for credible forensic reporting. The chain of custody (CoC) or chain of evidence, a vital legal document (protocol), provides safeguards against any manipulation or tampering with forensic samples. The chain of evidence accounts chronological documentation having detailed notes of seizure, custody, control, transfer and subsequent stages of analysis and disposition of evidence establishing authentic continuity of possession of a sample. The Court of Appeal of the State of New York had observed that “it is necessary to establish a complete chain of evidence, tracing the possession of the exhibit … to the final custodian, and … if one link in the chain is entirely missing, the exhibit cannot be introduced or made the basis for the testimony or report of an expert or officer.”
The chain of evidence protects against human error, securing probity and sanctity necessary for admissibility of evidence during court proceedings. During entire journey of forensic evidence from collection at crime scene to courtroom via forensic laboratory, the chain of evidence must be duly maintained in a logbook demonstrating that the sample was in legitimate custody at each stage. Indeed CoC represents series of documents such as courier receipts, laboratory logs and work sheets. The length of chain of custody varies in different jurisdictions as discussed in Ohio v. Conley.
The content of chain of evidence includes:
- Unique identifier
- Item description
- Identity of the person who collected the item
- Time and date of collection
- Acknowledgment with identity of persons who received the docket
- Description of docket movement
During criminal proceedings, prosecution has to eliminate every possibility of alteration, substitution or tampering of sample by establishing chain of evidence custody. However, in civil disputes, the burden of proving the custody chain rests on the party offering the evidence. In People v. Connelly28, the Court of Appeal of New York held that “Admissibility generally requires that all those who have handled the item ‘identify it and testify to its custody and unchanged conditions’ ’’. Minimum number of individuals must handle the docket and every time docket exchange hands, it must duly record on CoD documents.
Scientific investigation is a precursor to fair trial to ensure justice. DNA as unstoppable witness has proved its credibility in courtroom provided sanctity of biological sample is beyond any doubt. Negligence is no excuse in handling forensic samples since it may nullify the very purpose of forensic analysis and has potential to result in imperfect justice either by exoneration or false conviction of the accused. All stakeholders handling DNA sample in sexual offence cases need to be professionally educated and equipped with kits and procedural protocol for ensuring best usage of DNA evidence for assisting courts in pursuit for truth. Legal provisions must be in place making use of DNA technology compulsory in handling cases of sexual assaults to minimise possible misuse of oral testimony. The standard protocols for DNA sample is a futuristic step in the direction of administering perfect justice in cases of sexual assaults and other violent crimes.
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