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What is forensic science?

Updated Tuesday, 9 February 2021
We've all seen CSI, but what exactly is forensic science? Martin Bootman explains.

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Image of forensic scientists working in a lab. Forensic science, or forensics, is the application of science to establish how historical events occurred and thereby provide impartial evidence that can be used in a court of law.

Science can be defined as the collection of information through systematic experimentation and observation. Science often involves the detailed study of natural or man-made process in order to understand how and why they happen. Sometimes science proceeds simply by careful observation and the linking of concepts and ideas, but it may also require the development of technology and new experimental approaches.

The term forensic comes from the Latin word forensis, which refers to a Roman business place known as the forum. The forum was a busy site where civic meetings were convened and criminal matters were debated. People accused of a crime, and their accuser, would go the forum and their arguments were presented to the judiciary. Because of its historical connection, the word forensic is commonly used in modern language to refer to legal evidence that is presented in court.

The trustworthiness of evidence is crucial in criminal cases, and requires that the scientific methods used are reliable and accurate. The role of a forensic scientist is encapsulated by Locard’s Exchange Principle; a concept that is attributed to the medical doctor and criminologist Dr Edmund Locard. Locard’s Exchange Principle suggests that when a person enters a place that will become a crime scene they will leave behind distinguishing evidence, and moreover take some part of the scene with them. It is the job of forensic scientists to discover and verify the exchange of materials. In addition to his exchange principle, Locard is credited with starting the first crime laboratory in an attic within a Lyon police station during 1910.

The history of forensic science

Fingerprints taken by William Herschel 1859/60. Fingerprints taken by William Herschel 1859/60.

Forensic science was used to solve important issues and criminal cases long before the term was coined. Famous examples include Archimedes’ discovery that the amount of gold used in King Hiero II’s crown could be could be calculated by immersing the crown in water and measuring the amount of water it displaced, and the autopsy of the Roman Emperor Julius Caesar in 44 BCE that confirmed his death by blood loss.

In 1247, a Chinese magistrate called Sung Tzu compiled a volume entitled Washing Away of the Wrongs in which he described examples of post-mortem examinations and the appearance of bodies following different causes of death. Sung Tzu’s compilation is considered to be one of the first attempts to catalogue forensic observations and provide practical advice to investigators. Sung Tzu is also credited with the first reported case of forensic entomology, in which flies attracted to blood on a weapon were used to identify a murderer. The Handbook for Coroners, Police Officials, Military Policemen, written by the Austrian magistrate Hans Gross in 1893, is considered to be a watershed for the development of modern forensic science. In his publication, Gross combined different areas of criminal investigation such as psychology, photography and various scientific methods into a coherent guide. Gross argued for the standardisation of methods and a systematic approach to obtaining evidence in criminal cases.

Many branches of forensic science have developed over the past centuries in order to catch criminals, or prove innocence, in vastly different scenarios. They range from complex computer-based recreations of crime scenes, to laboratory-based investigations of tissue, fibres and DNA samples, through to relatively low-tech observations such as counting the number and maturity of insects invading a decaying corpse. It is common for evidence from several types of forensic science to be used in one case. The application of science to collection, analysis and explanation of evidence, allows a forensic scientist to reconstruct historical events, identify victims and pinpoint the perpetrators.


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