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What Is Locard Principle?

Introduction To The Principle

Do you know that anyone enters an area (the scene) he or she will leave a trace or takes something away? So if you do not want your presence to be discovered, do not leave a trace by touching any object.

This is the basic principle in the field of forensic; each physical contact will leave a trace.

Generally, this principle involves three major elements, victim, suspect and the crime scene.

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Based on this principle, when a crime takes place, there will be physical contact between victim, suspects and the crime scene.

When physical contact occurs, physical evidence or biological evidence is left by victim and suspect at the scene or they will be brought back when they leave the scene.

Physical evidence and biological evidence are like pieces of ‘ puzzle ‘ and need to pieced together to get a true picture of the crime that occurred at the scene, which is also known as the ‘crime scene reconstruction’

This evidence is considered as a ‘witness’ at the scene. Thus the chain of evidence should be preserved accordingly so that all evidences cannot be challenged.

Through the Locard principle, the status of the scene can be identified, whether it is a primary crime scene or secondary crime scene.

Primary crime scene refers to the place where the crime took place, while the secondary crime scene refers to all surrounding areas of primary crime scene.

For example, if the crime took placed in a bedroom of a home, the secondary crime scene would be all other rooms in the house as well as entry and exit areas in which the suspect may have traces of.

History Of Edmond Locard

Dr. Edmond Locard, a name widely known to those involved in the forensics field. He was born in 1877 in Lyon, France. In 1902, he obtained doctorate of philosophy (PhD) in medicine.

After that, Locard worked as the assistant for Dr. Alexander Lacassagne. A few years later, Locard began his first step by pursuing his career in law and passed the bar in 1907. He started his world travel one year after that.

During the First World War, Locard work in the French Secret Service as a medical examiner, where he was assigned to identify the cause and location of death of soldiers and prisoners based on stains and damage on their uniforms.

Locard created a crime laboratory in Lyon, France in 1910 and which officially opperated in 1912.

Throughout his life, he had served as a police officer in Lyon and published more than 40 articles and books in various languages ??including Germany, Spain and English.

Dr. Edmond Locard learnt a lot about forensics through his mentor Dr Alexander Lacassagne ‘ Father of Modern Forensics Medicine’ (1843-1924) and his partner, Alphonse Bertillon (1853-1914) known as Father of Anthropometry.

According to Locard, the evolution of the burden of proof is necessary through these 4 steps

  • Providence: Ordeals, Combats
  • Confession
  • Witness, testimony
  • Physical evidence

Locard stated there are five important elements in the thought process; detailed observation, proper and logical reasoning pertinence and significance of characteristic observed, the proper application of observation techniques, and interpretation of the result obtained

His contribution in the field of forensic is outstanding, the poroscopy invention where the pores in the papillary ridges of fingerprints are used as means of identification until today.

Besides that, he invented modified method of analysing blood stains and also systematized the analysis of the dust in the suspect’s cloth.

Application Of Principle

Who is at the scene? How to prove that a person was at the scene? What happened at the scene? All of these questions always play in the mid of investigator.

To answer all these questions, Locard principle is applied. So, what sort of evidence that may be encountered at the crime scene and is the evidence significant and can assist in investigation?


Fingerprint is the main evidence to detect the presence of a person at the scene. Base on the Locard principle, fingerprint can be detected if someone touches any object at a crime scene.

For example, in a robbery, a suspect has to hold the door knob to enter the victim’s house. So, the suspect’s fingerprints will be left on the door knob.

If the investigators manage to obtain and analyze that fingerprint, and be able to identify the suspect, it gives a lead in the investigation. This is how a Locard principle is applied in investigation.

There are two main characters that make the fingerprint evidence is reliable. Firstly, no two persons have exactly the same ridge pattern of fingerprint and secondly, the fingerprint patterns of any one individual remain unchanged throughout his life.

There are three types of fingerprint

  • Impressed fingerprint pressure – are indentations left in soft pliable surface, such as clay, wax, and paint. They are visible and can be viewed or photographed without development.
  • Visible fingerprint – also call patent print and are left in some medium, like blood, that reveals them to naked eyes
  • Latent Fingerprint – not apparent with naked eye. They are formed from the sweat from sebaceous glands on the body. The print must be developed before they can be seen or photograph using several technique such as dusting, fuming or chemical reagent

Hair and fiber

Back to the Locard principle, hair and fiber is another evidence that is capable to link between the suspect, the victim and the crime scene.

For example, a baby girl was found dead at home and a post-mortem was done. Investigator found that there was a head injury due to blunt force trauma to head.  The parent claims that, there was a monkey that took their baby and threw the baby down from a tree.

In the investigation, they found several hairs on the body and sent the sample for further analysis. Base on morphological analysis, the hairs are not human hair but it belongs to the monkey. So we can conclude there was a physical contact between the baby and the monkey.

Hair analysis is based more on morphology and characteristics. Every human hair varies depending upon individual morphology, colour and texture. There is even variation of hair morphology between different parts of same body.

Not so long ago, most fabric were made from wool, cotton, linen and silk but nowadays a wide variety of combination of fiber is used to create new fabric. Moreover, manufacture can also develop synthetic fiber as a new kind of fabric.

Indirectly, it makes the fiber analysis more difficult to identify the type of fiber found at the scene.

Normally, burning test and chemical test is the best analysis to determine the type and composition of fiber. Physical test such as strength test also help in identification process.

Blood stain

In a scuffle that resulted in injury cases, blood stain becomes important evidence to link between suspect, victim and the crime scene. The presences of blood stains on an implement give a clue to the investigator the type of object that has been used during the scuffle.

In that situation, again Locard principle plays a major role in an investigation.
What other information can be obtained from these blood stains?
Firstly, the identity of the person is known through Deoxyribonucleic acid blood test (DNA) analysis, whether the blood belongs to the suspect or victim. Secondly, the blood pattern analysis gives the information that can help investigators to reconstruct the crime scene (crime scene reconstruction)


Locard Principles founded by Dr. Edmond Locard help the investigation in correlating between the suspect, the victim and the crime scene. The evidence found at the crime scene should be analysed accordingly so that the suspect can be proved present at a crime scene.

Nowadays criminal are more advanced using the latest technology to commit their crime and knowing how to eliminate evidence of their presence at the crime scene. Therefore, the tasks of Forensic Scientists have become ever more challenging and they have to prepare themselves with the knowledge of forensics to bring the criminal to justice.

Last Reviewed : 21 April 2014
Writer : Mohd Faizul b. Abd Wahab
Accreditor : Sharifah Safoorah bt. Syed Alwee Al Aidrus