Short note on Forensic Medicine

By | September 11, 2023

Forensic medicine refers to the application of medical knowledge to legal problems. It involves the examination of areas of law and legal systems that interface with medical and scientific knowledge. Forensic medicine assists with evidence gathering and interpreting findings of forensic significance for legal purposes. Medical practitioners play a crucial role in forensic investigations by examining victims of violence or accidents, determining the cause and manner of death, and analyzing and documenting findings for use in legal cases. This note provides an overview of key areas of forensic medicine that are important for medical students to understand.

Role of forensic pathologists
Forensic pathologists, also known as medical examiners or coroners, are medical doctors who specialize in forensic pathology. Their main role is to perform medicolegal autopsies to determine the cause and manner of death in cases involving litigation, insurance claims, suspicious deaths, and homicides. During autopsies, forensic pathologists methodically examine the body both externally and internally for any signs of injury, illness or poisoning. They analyze organs, tissues, body fluids and collect other relevant forensic samples which are then examined using various medical and scientific techniques. Based on the autopsy findings and circumstances of death, forensic pathologists issue a report stating whether the death was natural, accidental, suicidal or homicidal. They may be required to testify in court about their findings and opinions. Forensic pathologists work closely with other forensic scientists as well as law enforcement agencies during death investigations.

Forensic entomology
Forensic entomology refers to the use of insect evidence in legal investigations. It can help determine the minimum period of time since death or postmortem interval. Certain insects are attracted to and feed or breed on a human corpse at different stages of decomposition. By identifying the insects present on or near the body and analyzing their developmental stages, forensic entomologists can estimate how long the body has been dead. Factors like ambient temperature, humidity and insect access also play a role. For example, the presence of fly eggs or 1st instar larvae suggests death occurred within the past 24 hours, while 3rd instar larvae point to a death 3-7 days ago. Entomological evidence has been used to solve criminal cases and contested insurance claims.

Forensic anthropology
Forensic anthropologists analyze skeletal remains both human and non-human to assist medicolegal investigations. They are valuable when only bones are available for identification. By examining bones, teeth and other remains, forensic anthropologists can determine factors like age, sex, stature, ancestry, and presence of any trauma. They also identify unusual bone features to estimate time since death. Anthropologists reconstruct facial features from skulls to create facial approximations that can aid in identification. In mass disasters, they assist in sorting and identifying fragmented remains. Anthropological evidence has helped solve missing persons cases, identify victims of war crimes and genocide. It also plays a role in differentiating human from animal remains as well as estimating postmortem interval.

DNA analysis
DNA analysis has become one of the most important forensic techniques due to its immense discriminatory power. Even a miniscule amount of biological material containing DNA can be matched to individuals with a very high degree of certainty. Forensic DNA profiling involves extracting DNA from blood, semen, saliva, hair or other tissues and analyzing specific locations on chromosomes called STR loci that are highly variable between individuals. The DNA profiles generated are then compared to samples from suspects, relatives of missing persons or criminal DNA databases to find potential matches. DNA evidence has been instrumental in solving rapes, murders and other violent crimes, and in exonerating wrongfully convicted persons. It has also helped identify victims of mass disasters. With new technologies like touch DNA and next generation sequencing, even smaller and more degraded DNA samples are providing crucial leads. While powerful, DNA analysis must be performed carefully following established scientific protocols and legal guidelines.

Forensic toxicology
Toxicology deals with the scientific analysis of drugs and poisons in biological specimens. Forensic toxicologists aid medicolegal death investigations and provide evidence about the role of drugs/toxins in alleged poisonings, overdoses and impaired driving incidents. Postmortem samples like blood, urine, vitreous humor, liver, stomach contents and hair are submitted for toxicological screening using techniques such as chromatography and immunoassays. Common analytes include alcohol, illicit drugs, prescription medications, volatile solvents, metals and biological toxins. Toxicology reports indicate whether intoxicating substances were involved in a death or incident and at what estimated concentrations. This information complements autopsy and circumstantial findings in determining cause and manner of death, proving intoxication in DUI cases, and resolving poisoning allegations in criminal matters. Toxicology labs must follow strict chain of custody and quality assurance protocols for test results to stand up in court.

Fingerprint analysis
Fingerprints remain the most widely used and judicially accepted form of personal identification in forensic investigations. No two persons share the exact same fingerprint pattern which makes it highly individualistic. Fingerprint examiners detect, document, enhance and analyze friction ridge features like ridge endings and bifurcations under a microscope to compare marks left at crime scenes to those found in fingerprint databases like AFIS. A definite identification is made when sufficient level and quantity of corresponding friction ridge details between two prints are found. Fingerprint evidence links suspects to crimes by placing them at the scene. It solves burglaries, thefts and other cases by matching latent prints recovered from crime scenes to those of suspects. While very reliable when following scientific standards, there are limitations in obtaining clear latent prints from some surfaces.

Firearm analysis
Firearms examination aids investigations involving shootings and recovered bullets/shell casings. Firearms examiners analyze gunshot residues, discharged bullets/cartridges under comparison microscopes, and test-fire submitted firearms to obtain evidentiary bullets for comparison of class and individual characteristics. Some class features used are caliber, rifling impressions and margins left by the gun barrel on bullets. Individualizing striations and marks imparted by imperfections in the gun’s firing mechanism provide stronger evidence for identification when corresponding striations are observed between evidentiary items. Firearm analysis is commonly used to identify the gun that fired bullets in homicides and link ammunition components recovered from crime scenes to guns seized from suspects. However, limitations exist as wear on older guns may reduce individuality of marks over time.

Trace evidence
Materials that are not readily identifiable under normal lighting but reveal microscopic characteristics which can associate persons or objects are termed trace evidence. Common trace materials examined include glass, fiber, paint, soil, gunshot residues and arson debris. Forensic scientists employ microscopic methods, instrumental analyses andPCR-based techniques to analyze recovered trace samples and compare them to known standards. For example, examining the refractive index, thickness, composition and other features of glass fragments using an analytical microscope can connect evidentiary glass to a potential source like thebroken headlight of a suspect’s vehicle. Proper collection, packaging and scientific examination of trace evidences can provide corroborating links between persons, places and events in criminal cases, hit-and-run incidents and more. Their value lies in narrowing down potential common sources.

In summary, forensic medicine encompasses a multidisciplinary approach incorporating principles of forensic pathology, forensic anthropology, forensic odontology, forensic psychiatry and various forensic laboratory analyses. It plays a crucial role in providing scientific evidence and expert opinions that assist legal proceedings. As future physicians, medical students should be familiar with key areas of forensic medicine and the role of forensic practitioners working at the interface of medicine and law. Understanding basic forensic principles equips doctors to recognize forensic implications when managing violent death cases, collect samples properly, document injuries accurately, and interact effectively with forensic teams. Ongoing advances in technology and collaboration among forensic disciplines continue expanding the scope and impact of forensic science in investigations and the judicial system.