The Medical and Behavioural Forensic Sciences

A forensic autopsy is performed by a pathologist with specific training in medicolegal death investigation. It differs from a clinical autopsy (done to understand disease) in that it is conducted within a legal framework: the findings may become evidence, the body is the scene, and every observation is documented for a potential court appearance. In most common-law jurisdictions the authority to order a forensic autopsy sits with the coroner or medical examiner, not with the family or treating physician.

The examination proceeds from external to internal. The external exam records injuries, marks, and the condition of the body. The internal exam opens the body cavities and examines the organs. Tissue samples are taken for histology. Blood, urine, vitreous humour, and bile are collected for toxicology. The pathologist records not only what is present but what is absent: the absence of expected injuries (e.g., no defensive wounds in a supposed struggle) is as evidentially significant as their presence.

Cause of death is recorded as the disease or injury that directly caused death, with any significant contributing conditions noted separately. Manner of death (natural, accident, homicide, suicide, undetermined) is a medicolegal judgement that incorporates the pathological findings alongside scene and circumstantial information. A pathologist who has not reviewed the scene investigation cannot reliably certify manner of death on pathology alone.

Forensic toxicology answers the question of what drugs or poisons were in a person's body, at what concentration, and what effect they would likely have had. It operates across two main contexts: post-mortem toxicology (to help establish cause or contribution to death) and human performance toxicology (to determine impairment at the time of an event such as driving or workplace accident).

Post-mortem toxicology presents challenges that antemortem testing does not. After death, some drugs redistribute from tissue into blood (post-mortem redistribution, or PMR), artificially elevating the measured blood concentration compared with what was present at the time of death. Morphine and tricyclic antidepressants are particularly prone to PMR. Toxicologists counter this by sampling from multiple sites (peripheral blood, vitreous humour, bile, hair) and by interpreting concentrations in the context of known PMR patterns rather than treating a single blood level as definitive.

• Blood (peripheral preferred): gives the closest approximation to antemortem levels; subject to PMR from central sites.
• Vitreous humour (fluid from the eye): well-isolated from PMR; useful for alcohol and some drugs; small volume limits the test menu.
• Urine: sensitive to a wider range of metabolites; less useful for quantification; may not be present in all cases.
• Hair: provides a time-line of exposure (approximately 1 cm of hair per month); distinguishes chronic use from acute exposure.
• Bile: concentrates some drugs and is useful when blood and urine are unavailable or degraded.

Forensic anthropology is called when remains are skeletal, fragmentary, or so decomposed that standard pathological examination is insufficient. The anthropologist constructs a biological profile from the morphology of bone: pelvic shape for sex estimation, epiphyseal fusion and degenerative changes for age at death, femur length for stature, and cranial and dental morphology for ancestry estimation. These are probabilistic estimates with stated ranges, not categorical identifications.

Trauma analysis is the other major contribution. Bone preserves the signature of perimortem injury (occurring around the time of death, when the bone still had collagen) differently from antemortem injury (healed or healing bone) and post-mortem damage (dry, brittle fracture patterns with no vital reaction). Sharp-force trauma on bone leaves smooth-edged incisions; blunt-force trauma leaves crushing and radiating fractures; high-velocity projectiles leave distinctive entry and exit characteristics in the cortical surface.

Forensic entomology uses the biology of carrion insects to estimate the minimum post-mortem interval. Blowflies of the family Calliphoridae are the key species: they detect volatile compounds from decomposition within minutes to hours of death and deposit eggs on accessible body openings. The developmental rate of the larvae through three instar stages and into pupation is well-characterised for different temperatures, and entomologists use accumulated degree days (ADD) or degree hours to back-calculate the minimum colonisation time and therefore the minimum time since death.

Forensic odontology applies dental science to legal questions. Its primary use is identification: teeth survive fire, decomposition, and submersion far better than most soft tissue, making dental comparison the standard identification method in mass fatality incidents and in isolated skeletal or burned remains. The comparison is between the dental record held by the decedent's dentist (X-rays, charts, treatment notes) and the teeth of the unidentified remains. A positive identification requires concordance of features and the absence of unexplained discrepancies.

Bite-mark analysis is the more contested application. The claim is that an injury pattern (on skin, food, or other substrates) can be matched to the dentition of a specific individual. Several US convictions based partly on bite-mark evidence have been overturned following DNA exoneration, and the 2009 NAS report and the 2016 PCAST report both found insufficient scientific basis for the claimed uniqueness of bite marks and the claimed reliability of the comparison method. Bite-mark analysis remains admissible in some jurisdictions but should be treated as investigative, not conclusive.

Forensic psychology and forensic psychiatry both operate at the intersection of mental health and law, though they are distinct qualifications. Forensic psychiatry is a medical specialty requiring a medical degree and psychiatric training; it focuses on diagnosis, treatment, and testimony about mental disorders. Forensic psychology, typically requiring a doctoral-level psychology qualification, covers a broader range of applied assessments and research. In practice the disciplinary boundaries overlap, and practitioners from both fields testify on similar questions across jurisdictions.

The core tasks include competency to stand trial (does the defendant understand the proceedings and can they assist in their own defence?), criminal responsibility assessments (was the defendant's mental state at the time of the offence relevant to their culpability?), risk assessment (how likely is this person to re-offend?), and treatment recommendations for offenders in secure settings. Eyewitness reliability, false confessions, and the psychology of jury decision-making are research areas where forensic psychologists contribute as expert witnesses on the limitations of testimonial evidence.