How a crime scene investigation works

How a crime scene investigation works

While the CSI are gathering evidence from the scene of a crime they have many things to take into consideration. Firstly the crime has to be reconstructed, they have to identify who did it and lastly the evidence has to be preserved for analysis and gathered it in a way that will make it work in court.

Tracing evidence

The CSI may use many items at a scene of a crime which can include a tweezers, knife, plastic containers with lids and a filtered vacuum. They will also have a kit which contains disposable gloves, face mask, booties, a gown and also a waste bag.

If the crime that was committed involves a gun, the CSI will gather clothing from the victim and whoever else was at the scene to the lab so they can be tested. The clothes are placed in sealed paper bags so that they can be transported to the lab. If there are any drugs or powders found at the scene, they are collected with a knife and each sample is sealed in a separate container. The substance will be identified at the lab and the test may determine if there was possession of drugs or whether the victim was killed because of this. Drugs and other unknown substances usually go to the chemistry lab and the hair is sent to the DNA lab.

Body fluids

Body fluids like blood, saliva, semen etc can be found at the scene of a crime. These pieces of evidence are identified and collected by the CSI using a scalpel, tweezers, scissors, UV light, sterile cloth and protective eye wear. They also have a special kit to collect blood samples from any suspects who were at the scene.

If there is blood on the body of a victim who is dead the CSI will get a blood sample using a sterile cloth and some water. If there is blood or saliva gathered from the body that might be belong to somebody else, there will be a DNA analysis performed by the lab so that the sample can be used at a later date to compare that with the one that was take from suspect.

The victim’s nails will also be scrapped as if there happened to be a struggle; the skin of the skin of the suspect might be under the victim’s nails. The CSI can also use a UV light to detect blood that has been cleaned off a surface. Also if there is blood found at the scene of a crime, they can determine what type of weapon may have been used by certain blood spatter pattern.

Hair and fibres

The CSI can use tweezers, combs etc to collect hair or fibres from the scene of a crime. For instance if they are dealing with a rape case and the victim is still alive, they bring the victim to hospital to extract any hair or fibres found on the victim’s body. The hair and fibres are then sealed in separate containers and transported to the lab.


To obtain finger prints there are tools used which can include brushes, tape, chemicals, powders, super glue and a magnifying glass. Fingerprints can be used to identify the victim of identify or eliminate the suspect from the crime.

When the CSI come across any evidence at a crime scene, they photograph it, log it, recover and tag it. There is an evidence tag which may contain information such as the time, date, location of discovery and who found the item. There is also a report written with all the information describing the crime scene.

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