Forensic science is the application of a broad spectrum of sciences to answer questions of interest to the legal system. Forensic science uses highly developed technologies to uncover scientific evidence in a variety of fields. The word forensic comes from the Latin word forensic (meaning “public”) and currently means “used in or suitable to courts of judicature or to public discussion or debate.” Forensic science is science used in public, in a court or in the justice system; so any science, used for the purposes of the law, is a forensic science.
The Eureka legend of Archimedes (287 to 212 B.C.E.) can be considered an early account of the use of forensic science. By examining the principles of water displacement, Archimedes was able to prove that a crown was not made of gold (as it had been claimed) by its density and buoyancy. The use of fingerprints as a means to establish identity occurred during the seventh century. The use of medical evidence to determine the mode of death began as early as the 11th century in China and flourished in 16th-century Europe. The combination of a medical and legal approach to dealing with crimes used in the United States today had its origin in England in the 12th century, when King Richard I established the Office of the Coroner. The American colonists instituted the coroner system, which still exists today. There is no federal law requiring a coroner to be a licensed physician.
Modern forensic science has a broad range of applications. It is used in civil cases such as forgeries, fraud or negligence. It can help law enforcement officials determine whether any laws or regulations have been violated in the marketing of foods and drinks, the manufacture of medicines or the use of pesticides on crops. It also can determine whether automobile emissions are within a permissible level and whether drinking water meets legal purity requirements. Forensic science is used in monitoring the compliance of various countries with such international agreements as the Nuclear Non-Proliferation Treaty and the Chemical Weapons Convention and to learn whether countries are developing secret nuclear weapons programs. However, forensic science most commonly is used to investigate criminal cases involving a victim, such as assault, robbery, kidnapping, rape or murder.
The medical examiner is the central figure in an investigation of crimes involving victims. It is the responsibility of the medical examiner to visit the crime scene, conduct an autopsy (an examination of the body) in cases of death, examine the medical evidence and laboratory reports, study the victim’s medical history and put all that information together in a report to the district attorney, the public prosecuting officer within a defined district. Medical examiners usually are physicians specializing in forensic pathology, the study of structural and functional changes in the body as a result of injury.
The medical examiner may call upon forensic scientists, who are specialists in these various fields for help investigating a crime. In criminal cases, forensic scientists often are involved in the search for and examination of physical traces that may be useful for establishing or excluding an association between someone suspected of committing a crime and the scene of the crime or victim. Such traces commonly include blood, other body fluids, hair, textile fibers from clothing, paint, glass, other building materials, footwear, tool and tire marks and flammable substances used to start fires. Sometimes the scientist will visit the scene itself to advise about the likely sequence of events and to join in the initial search for evidence. Other forensic scientists called toxicologists analyze a person’s bodily fluids, tissue and organs for drugs, poisons, alcohol and other substances. Yet others specialize in firearms, explosives or documents whose authenticity is questioned.
One of the oldest techniques of forensic science is dusting the scene of a crime for fingerprints. Because no two fingerprints are the same, fingerprinting provides a positive means of identification. Computer technology now allows law enforcement officers to record fingerprints digitally and to transmit and receive fingerprint information electronically for rapid identification.
DNA fingerprinting provides an excellent way to analyze blood, hair, skin or semen evidence found at the crime scene. By using an advanced technology method known as the polymerase chain reaction (PCR), a laboratory rapidly can clone, or multiply, the DNA from a tiny sample of any of these substances. This process produces enough DNA to compare with a sample of DNA taken from a suspected criminal.
Forensic science today is a high-technology field using electron microscopes, lasers, ultraviolet and infrared light, advanced analytical chemical techniques and computerized databanks to analyze and research evidence. For example, blood-alcohol levels can be determined by actual blood tests, usually through gas chromatography. In this method, the blood sample is vaporized by high temperature and the gas is sent through a column that separates the various chemical compounds present in the blood. Gas chromatography permits the detection not only of alcohol but also of other drugs, such as barbiturates, cocaine, amphetamines and heroin.
When a body is discovered in a lake, stream, river or ocean and the lungs are found to be filled with water, the medical examiner must determine if the drowning occurred where the body was found or elsewhere. A standard microscope that can magnify objects to 1,500 times their actual size is used to look for the presence or absence of diatoms, single-celled algae that are found in all natural bodies of water. The absence of diatoms raises the possibility that the drowning took place in a sink or bathtub, not where the body was found, since diatoms are filtered from household water during treatment.
A scanning electron microscope that can magnify objects 100,000 times is used to detect the minute gunpowder particles present on the hand of a person who recently has fired a gun. These particles also can be analyzed chemically to identify their origin from a particular type of bullet. Forensic examination of substances found at a crime scene often can establish the presence of the suspect at the scene.
Human bite marks also can serve as circumstantial evidence. Such bites may be found upon the body of a homicide victim or within pieces of food or other objects found at the crime scene, such as chewing gum. A forensic scientist can fill the impressions caused by these bites with liquid plastic. Upon hardening, the cast formed is an extremely accurate replica of the assailant’s teeth, which can be compared with a cast made from the teeth of the suspect.
Subdisciplines of Forensic Science
This is the application of various sciences to answer questions relating to the examination and comparison of biological evidence, trace evidence, impression evidence (such as fingerprints, shoeprints and tire tracks), controlled substances and firearms in criminal investigations.
This is the study and interpretation of financial evidence.
This is the application of physical anthropology in a legal setting, usually for the recovery and identification of skeletonized human remains.
This is the study and interpretation of economic damage evidence to include present-day calculations of lost earnings and benefits, the lost value of a business, lost business profits, lost value of household service, replacement labor costs and future medical care costs.
This is the study of the causes of failure of devices, vehicles and structures.
This deals with the examination of insects in, on and around human remains to assist in determination of time or location of death. It also is possible to determine if a body has been moved after death.
This is the study of the uniqueness of teeth.
Forensic Psychology and Forensic Psychiatry
These deal with the legal aspects of human behavior.
This is the science dealing with the investigation of use of firearms and ammunition.
This is the study of crime scenes when the victim is an animal, such as an endangered species or an animal illegally hunted or poached.
Forensic scientists work in laboratories, at crime scenes, in offices and in morgues. They may work for federal, state and local government, forensic laboratories, medical examiners offices, hospitals, universities, toxicology laboratories, police departments, medical examiner/coroner’s offices or as independent forensic science consultants. The minimum requirement is a bachelor’s degree in chemistry, biology, physics, molecular biology or a related science.