Every contact leaves a trace: The basis of forensics

Every contact leaves a trace: The basis of forensics

By Avril Eyewu-Edero Every time we shake someone, go into a room, use a computer, or kill a person, there is a high probability that you will leave either a biological, digital, trace or physical evidence of yourself at the crime scene. Every contact leaves a trace. Sir Edmond Locard’s (French criminologist) principle of exchange which is the basis of forensic analysis states that ‘Every contact leaves a trace’, the sole aim of a forensic scientist or criminal investigator is to find evidence(s) related to an offender at a scene and compare to he/she’s sample either from a database or evidence collected during or after apprehension. 

Every time you access the internet, you leave what we call a digital footprint, which like a fingerprint can be linked back to you. This method has been useful to track down internet fraudsters commonly known as ‘yahoo yahoo’. ALSO READ: Crime Scene Contamination: Difficulty for forensic Investigation in Nigeria We leave digital footprints when we use the internet and this contains data such as website visited, emails sent/received, information shared, internet service provider, approximate location, IP address, search history and more. 

More intriguing is that information such as your post on blogs, articles and photos shared, activities on Social media platforms such as Facebook, Twitter, Instagram are part of your digital footprint that can be linked back to you. In a case of murder, there are various pieces of evidence an offender could leave at the crime scene such as blood during a struggle, hair, fibre, fingerprints, bite marks, weapon and more. This evidence, when collected from the crime scene, analysed in a laboratory and compared to a database or evidence collected from an apprehended suspect could help to link the suspect to the crime.

 In sexual assault cases, biological evidence could be collected from the victim and matched to an alleged suspect. This theory is fundamental especially in sexual assault cases involving children as the consent defence won’t hold much water, and the assaulter would have to explain how his/her trace was found on the victim. The application of forensic is vast and as much as an offender tries to manipulate a scene or try to commit a perfect crime, there is always a trace that would likely be left, that is why it is important for investigators to be very open-minded and explore everything they see at a crime scene. 

This principle has continued to help the criminal justice system solve a lot of crimes in the world and it’s important that the criminal justice system in Nigeria begin to appreciate the fact that we need evidence that positively places a suspect at a crime scene. This starts with a thorough investigation and well-equipped laboratories to carry out a different forensic analysis. So next time you shake someone remember you have left a bit of you with them and taken a bit of them with you. So, every contact leaves a trace.