What does a crime scene investigator do?
In Britain, a crime-scene investigator (CSI) works for the police. Wherever a crime has taken place, they quickly come and collect all kinds of evidence before it can disappear or be removed. This is called ‘forensic’ evidence, which means it’s to do with a crime.
However, in the UK, CSIs don’t analyse that evidence themselves – they send it to a lab to be analysed. And they’re not actually police officers, so they can’t arrest anyone! But their evidence can make all the difference when it comes to finding a suspect and then proving that they did it.
When gathering evidence, CSIs use their eyes, cameras, videos, tape measures and scanners to look for, and record, things like fingerprints, hairs, fibres, blood, footprints and even bullets. As part of their job, they might:
- make sure that no one who’s not allowed can come into the crime scene and mess up the evidence
- take detailed measurements of what they find, like where the gun was in relation to the body
- figure out where a bullet was fired from, or where the criminal was standing when she pulled the trigger
- sketch a diagram of the scene, or take photos or video
- package up and label all the evidence which needs to be sent to the lab
- write reports for police officers which very carefully describe what evidence was found and what it might mean
- show the jury and judge in court what they found.
Find out more about what CSIs do.
What surveying techniques are used in crime scene investigation?
CSIs use all kinds of equipment to capture information about the crime scene. These can include:
- laser scanners – These create a 3D image of what’s there at ground level, so this could show the exact position of a body as well as things like spent cartridge cases from bullets. 3D models can be stored on a computer and then shown in court, so everyone can understand what the scene was like just after the crime happened.
- aerial mapping systems – These fly above the scene and show a lot of things at once from a bird’s eye view.
- tape measures and rules – These may seem simple, but they’re accurate ways to measure the relationships between objects at the scene. For example: how far was the knife from the doorway?
- photography and video – These capture what could be seen at the scene. They can also show things that are fairly flat (like blood spatter, fingerprints or hairs) which therefore wouldn’t show up on scanning imagery.
- underground radar mapping – Is there a body buried under the patio? Has someone buried the weapon to try and hide it? This is how to find out!
- How many pieces of surveying equipment can you spot? (Hint: They can be found on top of tripods, carried in a backpack, or attached to a vehicle, drone or helicopter.)
In the sky:
- A Riegl laser scanner under the helicopter (Grid 6D)
- A Riegl laser scanner on the LiDAR USA drone (Grid 6F)
- A Monsen Engineering drone (Grid 6E)
- A Riegl laser scanner next to the dead yeti. (Grid 2C)
- A Trimble SX10 laser scanning Total Station next to the crash scene (Grid 4F)
Carried as a backpack:
- A Leica Pegasus laser scanning system (Grid 2E)
On the ground:
- A FINDAR ground-penetrating radar system (Grid 1E) which can be an underground detective, discovering all kinds of things from pipes to gold and even dead bodies.
- An SLR camera – this isn’t really a survey tool, but it is very useful in documenting the crime scene, so we’re happy to have it as part of the team here! (Grid 3D)
Why do you think you need to measure and take photos of a crime scene?
- To record exactly what was at the crime scene as soon as possible after the crime was committed (before anyone can take anything away, or the wind or rain can wash it away). After all, it might be years before the case goes to court, and otherwise people might forget important details.
- To find clues and record them in a way that is so accurate, it can’t be argued with.
- To helpful people who don’t get chance to visit the crime scene, such as police officers, lawyers, the jury and judges. This might involve showing them pictures or a 3D visualisation on a computer.
- Sometimes, because they’ve taken all the measurements, CSIs can actually recreate a real-life crime scene, perhaps in a warehouse or the police car park! This can help people like police officers and the jury to understand what really happened. So they need photos and measurements to be able to recreate things correctly.
- To help figure out what happened when the crime was committed. Who did what, and with what, and when, and where, and maybe even why?
- To get such exact proof that it can be accepted as evidence in a court of law.
- To help the court make the right decision about whether a person is guilty or not guilty.
Find Piggle Wiggle the TopoDOT dog. What has she found? Could it be a piece of evidence?
She’s found a mince pie – lucky Piggle Wiggle! (Grid 3G)
Who killed the yeti? Can you guess?
(Hint: Look for some forensic evidence – bloody footprints, a mince pie trail or even some toilet roll)
It was the squirrel in the tree! (Grid 4I) How do we know it was him? Because of the evidence. For example:
- Mince pies
- Toilet roll found at both the crash site and the yeti crime scene
- The red paw prints lading to the tree.
What are the yellow numbered markers next to the yeti?
These show exactly where each piece of evidence was found. They could be anything from a footprint to a spilt coffee cup or a murder weapon. They help make sure that no one forgets to record that evidence, and also help to stop people walking all over the evidence or throwing it away by mistake.
Why are the crime scene investigators putting tape around the crime scene?
To make sure people don’t step inside the crime scene area and mess up the evidence. Only official CSIs are allowed in. Once they’ve finished, they will ‘release’ the crime scene to the police, who can then start investigating.
Why are the crime scene investigators wearing masks?
For two reasons:
- First, to protect the evidence. CSIs work with teeny, tiny things like fibres from carpets or clothes, or dust or or hairs. Simply breathing out while they’re taking a close-up photograph of that evidence could blow it away – and then it’s gone. That’s why they wear gloves and shoe-covers, too, so they don’t add their own fingerprints, shoe-prints or hair to the evidence, and confuse everyone.
- Second, to protect themselves. A crime scene might contain things like poisons, radiation or even nasty smells from bodies that died a long time ago. It could be unpleasant or even dangerous to breathe these things in.
Why do you think the green LSF Land Rover crashed?
At first glance, it looks like the Simon’s spaceship crashed into ir, but there’s actually more to it. Its seems like there’s a big pothole in the road, and the Land Rover’s wheel fell into it. Did you know that surveyors check the road for potholes and other types of damage? Either a surveyor wasn’t doing their job here, or something else caused this gigantic pot hole!