MLT GlobeForensic Science: Forensic medicine basics
20 Forensic Science MCQs on Forensic medicine basics with answers and explanations.
Which injury involves superficial loss of the epidermis caused by friction or pressure?
An abrasion is a scrape or graze limited to the epidermis. It may show the direction of force and the pattern of the object.
Which feature distinguishes a laceration from an incised wound?
Blunt force tears skin, leaving irregular, bruised margins with nerves and vessels bridging the wound. Sharp objects cut cleanly without bridges.
Why is a reference sample from the complainant included in a sexual assault evidence kit?
Intimate swabs contain the complainant's cells. Their reference profile allows analysts to identify and subtract it, leaving foreign contributors.
Traditional primer-derived gunshot residue particles characteristically contain which elements?
Primer compounds (lead styphnate, barium nitrate, antimony sulphide) form particles containing Pb, Ba and Sb. Heavy-metal-free ammunition may lack them.
A burn destroys the full thickness of the skin, including the entire dermis. How is it classified?
Full-thickness burns destroy epidermis and dermis, including nerve endings. They appear white or charred and are often painless.
Autopsy tissue for histopathology is routinely fixed in which solution?
Neutral buffered formalin cross-links proteins, preserving morphology. The volume should be about ten times the tissue volume.
An older bruise shows yellow discolouration. Which haemoglobin breakdown product mainly causes this?
Extravasated haemoglobin is broken down to biliverdin (green) and bilirubin (yellow). Bruise ageing by colour is imprecise and should be interpreted cautiously.
Gunshot residue should ideally be sampled from a living suspect's hands within a few hours of the incident. Why?
Most GSR particles are shed from the hands within a few hours by normal activity and washing. Early collection with adhesive stubs, and protecting a deceased person's hands with paper bags, maximises recovery.
How should conjunctival petechial haemorrhages found at autopsy be interpreted?
Petechiae result from capillary rupture under increased venous pressure. They occur in neck compression but also in cardiac deaths, severe coughing and others.
In a suspected drowning, what finding supports that the person was alive on entering the water?
Diatoms inhaled during active breathing enter circulation and reach closed organs such as bone marrow. Comparison with water from the scene increases evidential value.
In suspected drug-facilitated sexual assault, why should a urine sample be collected as soon as possible?
Drugs like GHB may be undetectable in urine within about 12 hours. Early collection, usually up to 120 hours post-incident, maximises detection.
Which technique is the accepted confirmatory method for gunshot residue on adhesive stubs from hands?
SEM-EDS simultaneously shows particle morphology and elemental composition, allowing individual characteristic particles to be identified.
Which findings indicate a person was alive during a fire?
Breathing during the fire draws soot into the airways and CO into blood. Pugilistic posture and heat splits occur in bodies burnt after death too.
In living young adults, which radiological assessment is commonly used for age estimation?
Ossification centres appear and fuse in a known sequence. Fusion of late-maturing sites like the medial clavicle helps estimate age in the late teens and twenties.
Which practice best reduces postmortem contamination of microbiology cultures at autopsy?
Bacteria translocate after death. Collecting early, searing the surface and using sterile instruments reduces contamination and aids interpretation.
Why is a patterned injury of forensic value?
Patterned abrasions or bruises can mirror features of an object, such as a tyre or buckle, helping link a particular object to the injury.
What morphology is typical of characteristic primer gunshot residue particles under SEM?
Primer residues condense from vapour into roughly spherical particles, typically about 0.5–5 µm. Morphology plus Pb-Ba-Sb composition supports GSR identification.
In children, dental age estimation methods such as Demirjian's are mainly based on what?
Developing teeth pass through defined mineralisation stages visible on radiographs. Scoring stages gives a maturity score converted to dental age.
Tissue from an autopsy is needed for DNA identification. Which sample is preferred?
Formalin and acidic fixatives cross-link and fragment DNA, reducing typing success. Unfixed, frozen tissue gives better-quality DNA.
How does a typical ligature mark in hanging differ from ligature strangulation?
Body weight pulls the ligature upward toward the knot, producing an oblique, often incomplete mark. Strangulation ligatures usually form horizontal, complete marks lower on the neck.