The first police officer to arrive at the crime scene is the one who sets up the yellow cordon tape, before doing anything else. The yellow tape is essential. It keeps curious onlookers out, which is essential not just for public order, but also to prevent the crime scene from becoming contaminated. Onlookers entering the scene would create a huge risk of essential evidence being destroyed. Once the tape is up and the crime scene has been secured, the police officer in charge will call for a Crime Scene Investigator to attend.
Collecting physical evidence
The Crime Scene Investigator will don a paper suit, to avoid adding contaminating materials for their own clothes or body to the area. They will be responsible for collecting physical evidence from the scene. This will be fibres, hairs, bullet casings or potential weapons. To make sure the scene remains as undisturbed as possible, they will clear a path to the scene, checking it for and documenting any evidence along the way. They will also be speaking to whoever was first on the scene, noting down any ways in which the scene might have been disturbed in those crucial first moments.
Dusting for finger prints is a cop show staple, but they’re not the only prints taken from a crime scene. The investigator will also be looking for tire tracks, footprints and any other marks or signs of struggle. Where possible, casts will be made of tracks and prints. Scraps of cloth, fibres from clothing and even bits of litter can be key in identifying the criminal, and so will also be carefully searched for and collected.
Documenting the body
If there is a body at the scene then this too will provide huge amounts of evidence, usually gathered by a forensic anthropologist. The position of the body will be documented by photography before the investigator gets to work. They will then scrape under the finger nails and collect any bodily fluids at the scene to help determine causes of death.
An overall impression
The investigator is also trying to look at the scene as a whole, to build up an idea of what might have happened there. This means that on entering a kitchen, for example, whether the kettle or hob is still hot is an essential detail to be checked out. Is a small window left open? Are items on the shelves disturbed?
Recording the scene
Photographing the scene is the final essential part of the investigator’s job. Photographs of how and where each piece of evidence was found will help the prosecution outline what they think happened to the jury. The investigator will put a number beside each piece of evidence and photograph it, before sketching the whole scene. Finally, the investigator will write up a report of exactly what they observed from the time they arrived at the scene.