Postmortem (FMT) Artefacts

Definition

• The Essentials of Forensic Medicine and Toxicology, 36th ed., p. 447

Classification

1. Artefacts introduced between death and autopsy
2. Artefacts introduced during autopsy
3. Toxicological artefacts

I. Artefacts Introduced Between Death and Autopsy

(1) Agonal Artefacts

• Regurgitation and aspiration of gastric contents is a common agonal artefact, occurring during the dying process. It is seen as froth and stomach contents at the nose and mouth.
• May also result from handling of the body, resuscitation, or convulsive movements.
• Key distinction: If food particles are found beyond the secondary bronchioles on histology, this indicates antemortem inhalation (not an artefact).

(2) Postmortem Hypostasis Artefacts

• Subconjunctival and scleral hemorrhages can appear as a result of hypostatic congestion in dependent areas and are a common autopsy artefact during reflection of scalp flaps - they are of no significance.
• Banding of the esophagus: Pale bands in the mucosa caused by postmortem hypostasis being prevented from settling (e.g. by clothing around the neck).
• Elastic underwear parallel marks: Pressure marks from tight clothing can simulate contusion abrasions.

(3) Animal / Insect Artefacts

• Rodent bites produce clean-cut lesions that can simulate incised wounds or stab wounds.
• Ant lesions: Extensive linear ant lesions around the neck can resemble ligation abrasions.
• Crabs and crustaceans tend to gnaw soft tissues around eyes, ears, mouth, genitals, and anus - may simulate antemortem wounds or enlarge existing wounds.
• Leeches attached near the eyes may produce hemorrhagic lesions simulating a black eye.
• Bodies in water may suffer mutilation from marine animals (fish, turtles), boat propellers, or blunt contact with rocks/coral - these must be distinguished from antemortem trauma.
• The Essentials of Forensic Medicine and Toxicology, 36th ed.

(4) Postmortem Hemorrhage

• Blood in the body remains in a fluid state for some time after death. Postmortem injury can open a blood vessel, causing postmortem hemorrhage.
• The finding of extravasated blood in the tissues does not necessarily mean antemortem trauma.
• Conversely, absence of gross bleeding does not necessarily indicate postmortem injury - in rapid vascular collapse (e.g., repeated stabbing with falling blood pressure), haemorrhage may be minimal even with antemortem wounds.
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology, p. 114

(5) Artefacts in Brain

Tip: To prevent additional artefactual flattening during fixation, brains should be suspended in 10% formalin by a hook passed around the basilar arteries for 3 weeks before dissection.

(6) Artefacts in Liver

• Greenish/blackish-brown discolouration of the undersurface of the liver at contact with the transverse colon - due to putrefactive substances (sulfides) passing from the bowel.
• Bile staining of the liver surface.

(7) Hyoid Bone Fracture

• Man-handling of neck structures by untrained morgue assistants can cause fracture of the hyoid bone, which is a postmortem artefact - it must not be mistaken for evidence of strangulation.

II. Artefacts Introduced During Autopsy

• P.C. Dikshit Textbook, p. 115; The Essentials of FMT, 36th ed.

III. Toxicological Artefacts

Faulty Sample Collection

• Drawing blood from the heart with a long needle can contaminate the sample with gastric contents - alcohol levels may be falsely elevated.
• In traumatic deaths (e.g. road traffic accidents), ruptured stomach can contaminate pleural/pericardial cavities with alcohol.
• Pericardial/pleural fluid may be withdrawn instead of blood, giving unreliable toxicology.

Faulty Storage

• Cutting organs with instruments contaminated by stomach contents.
• Storing multiple organs in one container - diffusion/drainage between organs alters true poison concentrations.

Use of Preservatives

• Preservatives such as EDTA and formalin can interfere with toxicological analysis and produce artefactual results.
• P.C. Dikshit Textbook, pp. 114-115

Key Medicolegal Importance

• The autopsy pathologist must always differentiate artefacts from true antemortem changes.
• Errors can be exploited in cross-examination by defence counsel to discredit medical testimony.
• A misidentification of an artefact as antemortem injury (or vice versa) can determine the freedom or imprisonment of an accused person.

"The responsibility of the autopsy pathologist is immense. Often, the doctor is the primary source of evidence upon which crucial legal decisions are based." - The Essentials of FMT, 36th ed., p. 447

• The Essentials of Forensic Medicine and Toxicology, 36th Edition (2026), Chapter 21
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology, Chapter on Artefacts
• Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology

DNA Test - Forensic Medicine (Narayan Reddy, 36th Ed.)

Definition

• Chances of two people having the same sequence: ~1 in 1,000,000,000,000,000 (one million billion)
• Even among siblings: only 1 in 10,000 million
• With recent advances, even identical twins can be differentiated
• Developed by Dr. Alec Jeffreys in 1985 - first used to solve two murder cases

Indications (Applications) - Four Main

Material Used for DNA Testing

• Blood (leucocytes - white blood cells)
• Seminal fluid
• Hair with root sheath cells (not hair shaft alone - must have follicle)
• Bone marrow
• Muscle
• Skin
• Brain tissue
• Dental pulp
• Dried stains (blood, semen on clothing)
• Vaginal smear
• Nails
• Tooth pulp

Red blood cells (RBCs) are anucleate and therefore cannot be used for DNA profiling.

DNA Typing - Procedure

Basis

Method 1: RFLP (Restriction Fragment Length Polymorphism) - Classical Method

1. Extraction: DNA is extracted from biological material (blood, semen, hair root, etc.)
2. Restriction Digestion: DNA is cut into fragments using restriction endonucleases (bacterial enzymes that cut DNA at specific sequences). This produces fragments of varying length - the VNTRs create the variation.
3. Gel Electrophoresis: The DNA fragments are separated by size by passing an electric current through an agarose gel. Smaller fragments travel further; larger ones stay near the origin.
4. Southern Blotting: DNA fragments are transferred from the gel onto a nylon or nitrocellulose membrane (a process called Southern blotting after its inventor E.M. Southern, 1975). The membrane is treated with alkali to denature (separate) the double-stranded DNA into single strands.
5. Hybridization with a Probe: A radioactively labelled DNA probe (single-stranded fragment of known DNA sequence complementary to the VNTR sequences) is applied to the membrane. The probe hybridizes (binds) specifically to its complementary VNTR sequences.
   • Multilocus Probes (MLPs): Detect variations at several genetic regions simultaneously. Produce a band pattern of 30-40 dark bands on X-ray film.
   • Single Locus Probes (SLPs): Analyze only one hypervariable location. Each SLP detects just two bands (one maternal, one paternal).
6. Autoradiography: The membrane is exposed to X-ray film. The radioactive probe produces a visible band pattern - the DNA "fingerprint."
7. Comparison: The band pattern from the evidence sample is compared with that from the suspect's sample. A match confirms identity.

Method 2: PCR (Polymerase Chain Reaction) - Modern Method

1. DNA Isolation: DNA is isolated from the sample.
2. Denaturation (94°C): The sample is heated to >94°C, splitting the double helix into two single strands.
3. Annealing (temperature lowered): Primers (short, specific DNA segments) bind to the polymorphic regions of interest on each single strand.
4. Extension (72°C): Temperature is raised to 72°C. TAQ polymerase extends the primers, copying both DNA strands and inserting complementary nucleotides (base-pair complementarity maintained).
5. Cycling: The cycle is repeated ~30 times, producing more than 1 million copies of the target DNA.
6. Detection: Amplification products for VNTR polymorphism are detected by electrophoresis, visualized by fluorescent detection or silver staining.

• Works on minute, degraded samples
• Very sensitive and specific
• Easily automated
• Can analyze 36 samples at a time
• Quicker

MLP vs SLP Comparison

Disadvantages of RFLP Method

1. Samples must be in good condition for analysis
2. Requires relatively large amounts of DNA
3. Time-consuming
4. Cannot be used on degraded or very old samples

Key Facts for Exams

• DNA fingerprinting: invented by Alec Jeffreys, 1985
• Southern blotting: invented by E.M. Southern, 1975
• India's DNA fingerprinting centre: CDFD, Hyderabad (uses Bkm probe from banded krait)
• Accuracy: near 100% (1 in 10¹⁵ chance of false match with MLP)
• RBCs cannot be used (anucleate)
• PCR = amplification method for degraded/small samples
• RFLP = classical restriction enzyme method for good quality samples