There’s a body in the cellar. A fire suspiciously broke out in the middle of the night. A famous artwork mysteriously vanished leaving a laughing emoji in its wake. Whatever the crime scene, an investigation now needs to take place.

Crime scene investigation (CSI) is the systemic examination of everything about the scene of the crime. It’s the way to discover every piece of physical evidence that can lead to the Who, What, Why and How.

Crime scene investigation

The Modus Operandi

The crime’s uncovered and the police swoop to the scene. It’s now a case of a bunch of clever, diligent, nit-picky, tech-savvy and observant souls working together to secure, document and examine the evidence. The mission: to be able to reconstruct the crime and figure out what happened.

This takes thoroughness big-style. No stone can be left unturned (figuratively or literally). Nothing can be missed. And it must all be done accurately to maintain the integrity of the evidence, enabling a conviction down the line. 

All crime scenes are different. Indoors, outdoors, homicide, burglary… there are always unique things to get to grips with. Nonetheless, there’s a basic process. 

Buckle up and see what happens with real crime scene investigation.

Crime scene investigation


Step 1: Set the dimensions

That glorious yellow tape that evokes secret excitement in you isn’t just an advert for rubberneckers. It’s setting out the dimensions of the crime scene and is the important first job when the investigators arrive on the scene. 

Think about it; set the scene too small and some local urchin picks up a crucial piece of evidence and wanders off, set it too big and you’ve got a lot of wasted time and effort going on. 

The first thing to do is to identify the focal point and create a perimeter containing the evidence. Bear in mind that it’s important to figure out the entry and exit points too. 

Act fast because you want to get most of these steps done concurrently, and before things go awry.

Step 2: Put security on the job

That local urchin who nonchalantly removes some evidence just-for-fun isn’t actually your biggest problem. There’s a good reason ‘returning to the scene of the crime’ is in common parlance. Criminals have a distinct habit of coming back to check things out. 

It can be a game, a way of reigniting the emotions they felt during the act, seeking a thrill, checking out how clever they and the detectives are, or wanting to mop up some evidence, but it’s not unusual. So security matters.

There’s also this really nifty standard called Locard’s Exchange Principle. The basic premise of this is that every person who enters or leaves the scene will add and/or take away material. Security helps to control access and control the complexity of an already complex scenario.

Crime scene investigation

Step 3: Figuring out the priorities

There’s a huge amount to do at a crime scene. There needs to be a quick run-down of the most urgent things.

What type of crime happened here? Have we got any threats to the evidence (weather, we’re looking at you)? Do we need any other hands to help out? Who needs telling about this? Does any suspicious individual or out-and-out perpetrator need rounding up first? Are there any hazards that need taking care of? Are those witnesses working themselves into a frenzy of exaggeration and need separating?

At this stage it’s actually helpful to develop a theory to work from. There’s no point trying to find evidence of a hit-and-run when the facts are pointing to a burglary.

Step 4: Get the right people there

Chances are that the bods who identified the crime scene won’t be the ones doing most of the graft. With a primary detective in charge of the case, lots of others will then be involved in working the crime scene.

This team will include photographers, evidence collection personnel, analysts and investigators. Crime scenes are busy places.

Crime scene investigation

Step 5: Begin the surveys

A quick scout of the crime scene needs to be done to identify the potential evidence. At this stage a photographer is all important.

They need to record everything exactly where it is in relation to everything else. Note-taking is also an important skill. These first impressions and records are often central to solving the crime.

Following a primary survey, more thorough documenting is necessary. 

Step 6: Collect samples and evidence

All of the evidence must now be collected and detailed. This is where procedural buffs are in their element. No evidence must be destroyed or contaminated in the process.

There is a huge variety of evidence that can be collected and used as part of the investigation including:

  • Biological evidence (that’s your body fluids, hair and skin cells under finger nails - anything that will reveal DNA).
  • Latent print evidence (this is anything from fingerprints to foot prints).
  • Trace evidence (stuff such as fragments of glass, bits of random vegetation and clothing fibres).
  • Digital evidence (valuable stuff such as emails, phone records and internet logs).
  • Drugs & firearms.
  • Tools (and marks from these).

The evidence that can and will be collected varies according to the crime and the nature of the scene. 

Crime scene investigation

Step 7: Go through it all again

We told you that CSI was all about thoroughness. At a crime scene investigation, a secondary survey is considered as important as the first. It’s quality control. Remember, what happens here has to be able to stand up in a court of law.

Step 8: Away from the scene

Once evidence has been gathered and recorded, analysis needs to start. Evidence will be sent off to forensic laboratories and external analysts, and detectives will set to doing other investigations based on evidence found at the scene.

This is where the ‘metry’s’ and the ‘ography’s’ get in on the act. There’s toxicology, serology, chromatography, spectrophotometry, mass spectrometry, forensic pathology and forensic entomology, just for starters.

All that’s now left is to use the evidence gained from the crime scene investigation to solve the crime.

If you want to be part of your very own crime scene investigation, why not find a CSI event near you today! 


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