At the scene of a crime

Everything at a crime scene could potentially be a piece of evidence. How do crime scene officers prevent contamination?
26 March 2015

Interview with 

Alan Dobson, Bedfordshire, Cambridgeshire and Hertfordshire collaborative major crime unit


What happens when the police arrive at a crime scene? How do they protect Scene of crime the evidence from contamination? And how do they decide what constitutes as evidence? Alan Dobson, a scene of crime coordinator with the major crime unit walks Chris Smith through how he would secure a scene...

Ginny - And so, our story begins. It was early this morning when the manager of the Cambridge Science Centre came upon the gruesome site now in front of us. As she entered the centre, she was surprised to notice that the door to the office, which was normally kept locked, was wide open. Crossing the room to look inside, she almost literally stumbled across the body of Mr. Wells, the centre's accountant, lying unmoving on the floor. Bending down to check his pulse, it didn't take her long to realise that the body was cold. 

Mr. Wells was dead. Shakily, she reached for her mobile phone to call the police.

(phone ring)

Police - Hello. You're through to the police. How can we help?

Female - I just got to work. I think somebody's dead. He's on the floor. He's not breathing.

Police - Okay. Are you sure he's not breathing? Have you checked? Can you see his chest rising?

Female - No. He's definitely not breathing. It looks like he's been here quite a while. He's not got a pulse either and he's cold. I'm pretty sure he's dead.

Police - Okay. Where are you? We'll get someone to you straightaway. Try not to touch him or anything around him, okay?

Female - Yeah. I'm at the Cambridge Science Centre, the one on Jesus Lane.

Police - Okay. Somebody's on their way. Stay on phone with me, okay.

Chris - So, what happens when the police arrive at a crime scene? How do they protect the evidence from contamination and what actually classes as evidence? Alan Dobson is a scene of Crime Coordinator with the Bedfordshire, Cambridgeshire, and Hertfordshire Collaborative Major Crime Unit. Easy for you to say. Welcome, Alan. Thanks very much for joining us. So tell us first of all, when you arrive at a scene like our one here, what actually do you do?

Alan - Well, I think the first thing that we have to ensure is that we have complete security of the scene. You'll see here already where you've placed the body, there are a number of items, which I won't discuss quite yet, because I don't want to come in to this scene prior to making sure that it is protected. 

There could be untold secrets here that we can look out, that we can provide evidence for. Until I have a full scenario of exactly what I believe has happened from all the people that had already been in, for example, the person finding the body, maybe paramedics. 

You can see here we've already put "crime scene do not enter" tape. We would have somebody on the other side of that with a crime scene log. That log will show every single person coming in and out of this scene. Quite simply, until I were to arrive with the crime scene manager, absolutely, nobody else comes in this scene.

Chris - How do you stop it getting contaminated?

Alan - Literally, by having police officers wherever we need to ensure that a particular area is guarded and anybody wanting to come in would have to have legitimate reason to. Until as I say, I'm there, there is no reason for anybody as long, as health and safety and fire and everybody else that may need to come in to make sure it's safe, nobody else would be allowed in.

Chris - What about the people who have to go in?

Alan - The people that have to go in would look like you Chris. Very nice in your white suit.

Chris - I should explained. You have geared me up. I'm actually wearing some lovely booties, which have gone over my shoes and I'm wearing - well, suppose it looks a bit like I'm going to treat an Ebola victim actually. It's a white 3m suit and face mask, a hood.

Alan - Indeed, yes - everything including your gloves, which would stop you contaminating my crime scene.

Chris - What could I bring in with me that might contaminate your crime scene?

Alan - You could bring in anything from shoe marks if you haven't got proper protection on your feet. You could bring in DNA from not having gloves on. You could bring DNA from as we speak, whilst you won't see it, saliva will leave your mouth and could contaminate a body. So, if we end up swabbing this deceased and finding some DNA, if it's yours, I'm not going to be very happy because I would suspect you're involved in the crime.

Chris - Oh dear! What about the fact that people, when they commit a dastardly deed, they tend to clean up after themselves, don't they?

Alan - Occasionally, depending on the type of crime scene. I mean, 31 years, I've seen basically - you name it, I've seen it. From putting chemicals all over to cleaning down thoroughly bodies even missing, to the one of domestic type assaults or murders whereby everything is left exactly as it is and somebody has probably phoned us to say, "Look, I'm sorry. I've committed this crime anyway." Where we don't have suspects, we may very well find cleaning up. But sometimes that's to our advantage.

Chris - Let's think for a minute then about what we consider to be evidence. Perhaps we could ask our audience. Can we have some suggestions please - if you could raise your hand and Ginny will come to you - can you suggest to us, what would you think we would judge to be evidence in a crime scene? Who would like to start the ball rolling for us?

Amelia - Amelia, fingerprints.

Chris - There's another one there...

Lily - Lily, hairs.

Tim - I'm Tim, footprints.

Chris - Anymore suggestions?

Ailish - Hi, I'm Ailish. I would say blood samples or saliva.

Frez - I'm Frez and I think a weapon.

Milly - Milly, fabric.

Female - You'd find a body sometimes.

Chris - You may even find a body and there's one more over here.

Ciana - Ciana, a broken window.

Chris - These are all good suggestions, Alan. Anything that people are missing that are obvious choices?

Alan - Within this scene itself, I would say everything that has been said is absolutely perfectly right - points of entry, how has somebody got in, has this person actually been murdered, do we know that yet? 

It's very easy for us at the moment to suspect that but is it somebody that's maybe committed suicide? Is it somebody who's maybe eaten something? Is it a natural cause? 

We don't know yet. What we would do is treat this as a crime scene. 

Now looking at this to start with, if I described a scene too on the crime scene side of the tape, we have the deceased lying face down. We have a laptop computer, which appears to be under his right arm and towards his left arm, not gripping but still stood up in the position, is a flask with the lid off. 

So initially, we're looking at possibly, what's on the laptop. Now under new forensics, we will have to send that off. It's not something that I would look at here. But prior to doing anything with that, we maybe need to look at DNA. We'd need to look at fingerprints. So we would swab it. We would - what we call - gel lift which is a particular way of taking fingerprints. And really quite soon, we'd get that from our crime scene to a lab for our techy experts to look into it and see what he's been looking at, what's he been dealing with. 

Bear in mind, this is a man who's dealing with money and the accounts of the university. Is that something that might be in this? Is there a fraud going on? We just don't know. So, we have to presume the worst. 

For me, that's a really essential piece of getting that done at the scene, to get away, to see what we've got. 

Really, the next part for me is the flask. What's he been doing? Has he been drinking from it? Could it be toxic? Is there something I need to be worry about? If it is toxicology we're looking at, clearly, that's not my remit here. I know we'll come on to that later but I would need to let the pathologist know that I've got a flask, I don't know what's in it yet. That will go to the chemical experts to tell me what we've got. 

Finally, we've got of course the whole body. Let's have a look at it. Is there anything else there that we may be missing? We need to look under the clothing. Could there be stabbed wounds? Could there be bruising? Could there be DNA on the fingers? Fingerprints - yes, that was mentioned. What about hairs? Maybe he's fought somebody. There could be somebody else's hairs within his nails. There's a whole remit. 

If I'm being honest with you, looking at this scene that we have here, I would estimate two scenes of crime offices probably the best part of 4 to 6 hours before they even start moving that body, to get the best forensics from where we are at this time.

Chris - Do you take sort of video footage of yourself going through a scene these days or is it just static photographs?

Alan - No. We do 3 things now. One is, normal photography, one is video and one is what we call R2S which is Return To Scene. It's a 3D spherical system that we would put footplates in anyway on our scene. That will enable anything that's under there that we don't know yet it's there because maybe some chemical treatment would bring fingerprints up on a floor like this. 

So because we don't know what's there, we would protect it by using footplates. The R2S, the Return To Scene photography system would then sit on top of that. We do a whole spherical. We can add things to that then so I can add evidence. We can eventually put the hard copy of photos into that to put the body to the scene. We could do the computer to show where exactly that was. 

As the forensic evidence comes to us, we can then start inputting that bit of evidence. So eventually, that will give you a whole scene. That may take several weeks, several months when toxicology comes back in but it will give you the whole picture, which we do ultimately need to show to a jury to prove or disprove that somebody has committed a crime.


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