Medico-Legal Autopsy: Procedure and Techniques

The pre-autopsy phase is the part of the procedure most consistently abbreviated in practice. In India, the BNSS 2023 § 194 (replacing CrPC § 174) requires the First Information Report, the inquest panchanama, and any available medical records to accompany the body to the mortuary. In England and Wales under the Coroners and Justice Act 2009 and HM Coroner's Rules, the pathologist receives a case history and any pre-mortem hospital records before examination begins. In the United States, the National Association of Medical Examiners (NAME) 2018 position paper on autopsy adequacy states that a complete autopsy requires documentation review prior to incision.

The pre-autopsy record review serves three functions. First, it generates a differential before the body is touched, focusing the dissection on the relevant systems. A history of treated coronary artery disease means the coronary ostia, main stems, and left anterior descending artery receive particular attention. A suspected stab-wound case means the clothing is retained as an exhibit before it is removed, and the wound track is examined before any tissue is displaced. Second, the pre-autopsy review identifies what special samples should be collected: a suspected poisoning requires vitreous humor, peripheral venous blood, urine, gastric contents, liver, and bile, in that order of collection priority, before any dissection disturbs post-mortem drug redistribution. Third, it establishes the jurisdictional context: in India, a medico-legal case requires the body to be identified by the investigating officer in writing before the autopsy begins; in England and Wales, the coroner's authority to proceed with autopsy must be confirmed.

Photography begins before the body is undressed. The sequence is consistent across major autopsy suites: body bag label, external body tag, clothing in situ, then clothing removed. In firearms and sharp-force cases, the spatial relationship between a wound in clothing and a wound in skin is lost the moment the garment is taken off, making pre-removal photography non-negotiable.

External examination follows a fixed anatomical sequence that must not be shortened because the case appears straightforward. The sequence used at AIIMS New Delhi and in the UK RCPath autopsy guidelines is: height and weight measurement, general body habitus, state of nutrition, evidence of medical intervention (cannulae, surgical scars, implants, therapeutic bruising from resuscitation), post-mortem changes (livor, rigor, decomposition state), and then a systematic head-to-foot wound survey.

Post-mortem changes at the time of autopsy are clock data. Fixed lividity indicates a post-mortem interval of at least six to eight hours since lividity fixes at that threshold under normal temperature conditions; unfixed lividity in a body reported found in bed means the position reported is plausible. Rigor mortis, assessed by joint resistance, documents the stage of the primary post-mortem change cascade. In Indian summer conditions (35-38 degrees Celsius ambient), rigor may complete in three to four hours and resolve by twelve to fourteen hours, substantially faster than the textbook eighteen-and-twenty-four-hour thresholds derived from temperate European studies. A pathologist applying European TSD nomograms without adjusting for local ambient temperature will produce an unreliable time-of-death opinion.

Wound measurement at external examination uses a millimetre-graduated ruler placed parallel to the wound in the photograph. Every wound receives a reference measurement from two fixed anatomical landmarks (for example, "5 cm below and 2 cm to the right of the right nipple"). This dual-landmark system, standard in NAME-compliant US autopsy practice and in RCPath UK reporting, allows the wound location to be reconstructed from a body diagram even years later during an appeal hearing.

The external genitalia receive specific documentation in all suspected sexual-offence deaths, as required by the BNSS 2023 framework for cases within the purview of BNS 2023 §§ 63-71. In such cases the Modified Goa Medical Protocol (India), the US SANE examination standard, and the UK Faculty of Forensic and Legal Medicine (FFLM) guidelines all specify that a vaginal smear and perianal swab are collected at this stage, prior to any internal dissection that might introduce contamination.

The standard internal examination sequence opens the cranial cavity last, after thoracic and abdominal dissection, in order to prevent brain tissue from contaminating other samples. In cases where cranial pathology is the primary question, many pathologists reverse the sequence, examining the cranium first and separately; the RCPath guidelines and the NAME autopsy adequacy criteria both allow this flexibility, provided the rationale is recorded.

Thoracic cavity examination begins with the removal of the sternal plate after recording the rib fracture pattern (ribs are a pressure-injury record in resuscitation cases). The pericardial sac is opened and pericardial fluid volume documented. The heart is examined in situ before removal: cardiac silhouette, coronary anatomy on the epicardial surface, and the patency of major pericardial veins. After removal, each coronary artery is sectioned at 3 mm intervals, the standard interval that reliably detects a critical stenosis above 75 per cent luminal occlusion. Lung examination documents the pleurae, lung weight (normal values: right 450-550 g, left 375-450 g), and parenchymal cut surface. Pulmonary oedema fluid is quantified, not simply noted as present.

Abdominal cavity examination documents fluid (blood, bile, gastric content, ascites) before any organ is displaced. Gastric contents are measured and retained: in suspected poisoning cases, 100 mL minimum, or the total available volume. The liver (normal 1,200-1,500 g), spleen (normal 150-200 g), and kidneys (normal 120-150 g each) are weighed; weight deviation documents chronic disease or acute congestion. The AIIMS Standard Operating Procedure for medico-legal autopsies specifies that the pancreas is examined and sampled regardless of suspected cause of death, because pancreatitis-related deaths are consistently under-documented in routine practice.

Cranial cavity examination documents subdural and extradural haemorrhage volumes, noting whether bridging vein tears are present (shaken-baby indicator), the degree of brain swelling, and the condition of the circle of Willis. Brain weight (normal 1,250-1,400 g in adults) is recorded after formalin fixation for neuropathological examination where indicated. In suspected head-injury deaths, slicing the brain fresh at 1 cm intervals after fixation is the standard practice at the National Forensic Science Laboratory (NFSL, India) and the UK Neuropathology Best Practice Advisory Group protocol for forensic cases.

Spinal dissection is performed in all cases where spinal injury is suspected and in all hanging cases, to document ligamentous injury, disc prolapse, and vascular injury to the anterior spinal artery. The NAME criteria for a complete autopsy include spinal examination in hanging cases.

Several sampling procedures fall outside the routine dissection sequence and require explicit planning before the autopsy begins.

Vitreous humor collection is performed by inserting a 23-gauge needle at the outer canthus of the eye under slight suction from a 5 mL syringe. The vitreous should be centrifuged and the supernatant frozen at -20 degrees Celsius within four hours for reliable vitreous potassium measurement. Vitreous from both eyes should be collected separately because asymmetric post-mortem changes (one eye exposed to light, one not) can produce slight bilateral differences.

Sexual-assault sampling in a death investigation follows the same SAFE-kit protocol as a living examination in India's Modified Goa Medical Protocol, with the addition that swabs collected from a deceased victim must be collected before any dissection begins. The vaginal vault, cervical os, perianal region, and sub-ungual scrapings are collected, sealed with tamper-evident tape, and signed by the pathologist and a witness before they leave the autopsy suite. The UK FFLM Protocol for Sexual Assault in Deceased Victims and the US SANE-D (SANE in Death Investigation) guidelines follow the same pre-dissection collection rule.

Ante-mortem dental record comparison at autopsy involves the attending odontologist or the pathologist documenting the dental status using the FDI two-digit notation (or Palmer notation in older UK records), recording present teeth, restorations, crowns, missing teeth and prostheses. This documentation is compared against ante-mortem dental records if available for identification purposes. In DVI contexts (see the INTERPOL DVI topic in forensic biotechnology), this becomes Phase 2 Pink Form data. In single routine medico-legal cases, dental documentation identifies an unknown body and confirms identity of a known body. The AIIMS Department of Forensic Medicine SOP and RCPath guidelines both require dental charting as part of every autopsy on an unidentified body.

Neonatal and infant autopsies include three additional special procedures: the hydrostatic test (Galenic test) for lung flotation to distinguish live birth from stillbirth, middle-ear examination for haemorrhage in suspected shaken-baby cases, and retinal examination for vitreal haemorrhages. These procedures are specified in the NAME guidelines for infant autopsy (NAME 2019), the RCPath Perinatal Guidelines (3rd edition), and the AIIMS paediatric forensic pathology SOP.

Chain of custody for biological samples in Indian medico-legal autopsy practice is governed by BNSS 2023 § 194 (formerly CrPC § 174), which authorises the Magistrate to request medical examination and directs the medical officer to submit findings in the prescribed format. The sample documentation requirements that flow from § 194 are supplemented by the DFSS Standard Operating Procedure for Viscera Preservation and the Indian Evidence Act framework now recodified as the Bharatiya Sakshya Adhiniyam 2023.

In the United States, the NAME autopsy adequacy document specifies that toxicology samples must be labelled with the case number, date and time of collection, and the collector's initials, and that the chain of custody must be maintained from collection to the receiving laboratory. Most US ME offices seal samples with evidence tape and require two signatures on the chain-of-custody form. In England and Wales, the Forensic Science Regulator's Codes require an unbroken audit trail documented on a specific exhibit label, with the exhibit reference traceable to the autopsy report.

The standard Indian viscera exhibit package comprises a sealed glass jar of stomach with contents (100-200 g), a sealed glass jar of liver (100-200 g), a sealed glass jar of one kidney (50-100 g), a sealed glass jar of vitreous humor from both eyes, a labelled blood tube (10 mL peripheral venous blood, typically femoral), and a labelled urine sample where obtainable. Each jar is sealed with adhesive and signed by the pathologist and the accompanying police officer. The sealed exhibits are handed to the investigating officer under a formal receipt, and this receipt forms part of the judicial file.

Post-autopsy handling of exhibits is among the most frequent sources of chain-of-custody challenges in Indian criminal cases. The Supreme Court of India in Sharad Birdhichand Sarda v. State of Maharashtra 1984, though a pre-BNSS case, established the five golden principles (Panchsheel) governing conviction on circumstantial evidence: each circumstance must be firmly proved, the chain must be complete, and every hypothesis other than guilt must be excluded before a conviction can stand. Post-BNSS, the requirements under § 194 are clearer, but the vulnerability remains wherever the chain between the mortuary seal and the FSL receipt seal is not continuously documented.

Several death categories require systematic modifications beyond the standard three-cavity examination, which must be noted in the pre-autopsy plan and recorded in the report.

Drowning cases require diatom extraction from lung, spleen, and femoral bone marrow, using the Pollanen 1998 acid-digestion protocol. The vitreous sodium-to-potassium ratio provides an additional drowning marker; the full medico-legal interpretation of drowning including wet vs dry subtypes is covered separately. Both the AIIMS forensic medicine SOP and the UK Forensic Science Regulator guidance on drowning include these as required special procedures.

Firearm cases require track dissection before any cavity is opened. The bullet track must be followed from entry through all intervening structures to its terminus or exit, with each structure traversed documented in sequence. The intermediate ballistics range-assessment uses the distribution of soot, tattooing, and stippling around the entry wound, and any of these can be obliterated by the removal of organs that carry them into the mortuary.

Decomposed cases require full skeletal survey at autopsy: the post-mortem interval will extend beyond the period when soft-tissue findings are interpretable, and skeletal injury (rib fractures, hyoid fracture, long-bone fractures) may be the only surviving physical evidence. The NAME guidelines and the RCPath guidelines both specify that decomposed bodies should receive a full skeletal radiological survey before dissection begins.

Toxicological death cases where poison is suspected change the sequence of cavity opening. In suspected oral poison ingestion, the abdomen is opened first and gastric contents are aspirated before the stomach is moved, preventing redistribution of gastric contents into the small bowel and peritoneal cavity.

The Vollum modification of the Virchow technique examines the wound track in relation to each organ before removal, and is described for use in firearm deaths. The Mayet variant of the Rokitansky technique adds an earlier skeletal survey step for putrefied bodies. Both are refinements documented in specialist forensic pathology texts; neither changes the fundamental principles of the underlying technique.

1. Pre-autopsy review
   FIR / inquest panchanama (India BNSS § 194) or coroner history (UK) or ME case brief (US); identify required special samples before incision
2. External photography
   Body bag label, tags, clothing in situ, post-mortem change documentation, wound survey with dual-landmark measurements
3. Special samples first
   Vitreous humor (before skull opening), sexual-assault swabs (before dissection), gastric aspirate in suspected poison cases
4. Thoracic cavity
   Sternal plate with rib fracture note; pericardial fluid volume; coronary artery cross-sections at 3 mm intervals; lung weights and consolidation map
5. Abdominal cavity
   Document fluid in situ; gastric contents volume and retain; liver, spleen, kidney weights; pancreas examination; mesenteric vasculature
6. Cranial cavity
   Subdural / extradural haemorrhage volumes; brain weight after fixation; circle of Willis for aneurysm; spinal dissection in asphyxia or trauma cases
7. Tissue and toxicology samples
   Seal exhibits per BNSS § 194 (India) / NAME protocol (US) / Forensic Science Regulator Codes (UK); sign chain-of-custody form with attending officer
8. Dental charting
   FDI two-digit notation; compare to ante-mortem records for ID confirmation or complete for DVI Pink Form registration