By Avril Edero

In 2015, I was called to help the law enforcement agents to lift fingerprints from a company in Lagos where some laptops were stolen.

On getting to the crime scene, there was a full palm print on the wall, we were excited that this would be an easy ride once we collect the print.

Our plan was to also collect fingerprint from all the staff and hopefully find a match. We started the normal crime scene process by obtaining information about the incident.

The security personnel narrated how they found out about the theft and the print when suddenly all hope was deflated.

Why? The security personnel said he had told all the staff present to place their palm on the palm print on the wall to check whose palm fits perfectly, in hope of ascertaining who the perpetrator is.

At that point, we had to explain the difficult truth, the crime scene had been compromised and there was no need going ahead.

I remember I had to explain to everyone including the law enforcement officers that the chances of knowing the culprit through the print at the scene are almost impossible.

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The multiple prints that would be on the palm print on the wall would make it difficult to determine who the exact perpetrator is, and the evidence would not be admissible in court.

This brings us to the particular issue of crime scene contamination.

A crime scene is a place where a crime/incident such as theft, armed conflict, murder, fire, suicide, rape, accident, etc. has occurred.

A major principle that governs crime scene analysis is the belief that every contact leaves a trace, that is,  every time we come in contact with anyone or

anything, we leave a trace of ourselves and take a trace of the person or thing with us. This is called Locard’s principle of exchange in Forensic Science.

From an incident scene, different traces are left, one can find evidence relating to the incident that can help provide understanding on how the crime was committed, interpret the facts, reconstruct the event, find out when the crime was committed, who was involved in the crime, what was used to commit the crime, and why the crime was committed.

Types of evidence that can be retrieved from a crime scene include biological evidence (e.g. blood and semen for DNA), trace evidence (e.g. hair and fiber), digital evidence (such as mobile phones and laptops), document evidence, ballistic evidence (e.g. bullet to match a weapon used to commit a crime), insects to determine time of death, etc.

Due to how fragile some of this evidence is, their reliability and preservation depend largely on how the incident scene is initially managed.

Forensics starts at the crime scene. Ensuring a crime scene is left as it is, is one of the greatest challenges we face, mainly due to lack of awareness.

If that crime scene I visited in Lagos had not been contaminated, we would have been able to lift fingerprints and would have had a good chance of narrowing down the suspect pool.

This is because the fingerprint is unique forensic evidence as no two people in this world have the same fingerprint. So, of all the approximately 8 billion people on earth, you won’t find anyone else with your fingerprint, therefore it is essential evidence in detecting the perpetrator of a crime.

One of the most prominent examples of the effect of crime scene contamination was the O.J. Simpson case in the US when his ex-wife Nicole Brown Simpson and her boyfriend, Ron Goldman were found murdered in their home.

Some key evidence such as a bloody fingerprint found at the crime scene was inadmissible in court due to crime scene contamination.

Human reaction and response to crime incident in Nigeria is usually a pandemonium which makes disaster management and scene preservation tough.

The normal reaction when an incident occurs is for people to troop to the scene to look at what happened, record videos, congregate at the scene which sometimes prevents life-saving help.

This, in turn, contaminates the scene and reduces the integrity of the forensic evidence that can be collected to identify how or why the crime has been committed or to trace the perpetrator of a crime.

Although forensic science is gradually gaining prominence in developing countries like Nigeria, it is important that we start making conscious efforts to avoid contaminating a crime scene.

Immediately an incident is reported or detected, life-saving measures (such as providing first aid for any injured person) should be taken if required in a careful manner without compromising the scene before and upon the arrival of the law enforcement agency, access into and out of the scene should be carefully managed, and crowd should not be allowed to congregate around the scene.

Anyone accessing the scene should wear protective clothing especially a glove before touching anything at the crime scene. Items from the crime scene should be appropriately collected and stored with the required documentation to ensure a chain of custody.

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In protecting a crime scene, the protected or cordoned zone should be free off non-investigators such as the press, relatives, etc.

The suspect can point at the crime scene where the evidence is (e.g. the dead body), but should not be allowed to touch the evidence so it will be easier to link evidence such as DNA and fingerprints found at the scene back to them and avoid the situation they would claim that their DNA only got to the crime scene when they took the police there.

It is also important that the law enforcement agencies, who are always the first responders are trained in crime scene management as they are usually responsible for collecting forensic evidence, so the contamination issues can be managed.

If everyone can understand and practice this simple concept of preventing crime scene contamination, it will be easy to obtain evidence that can be used to identify a perpetrator and seek justice.

So next time you witness an incident, you can do your bit to educate people to avoid contaminating the scene to ensure an effective forensic investigation.

Avril Edero is a forensic Investigator

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