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Asked by jonybraly to Anna, Craig, Richard, Shane, Sue on 21 Jun 2011.
Question: What procedures must you carry out when doing a simple forensic crime investigation?
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Craig McKenzie answered on 17 Jun 2011:
Hi Jonybraly,
That is a really good question and would depend on the type of investigation you were doing. I will give you one example and try not to waffle on too much!Crime scene investigation:
When we attend a crime scene we must be very organised, careful and thorough.
We get as much information as possible before we arrive or before we go into the crime scene. this is called ‘context’ we would work with the police, pathologists and any other experts who have arrived before us – i often worked with fire brigade people.. it will help to know this so we can plan our work.
When we arrive we assess how dangerous the crime scene is, what we know about initial victims and any possible suspects and we work out a plan for what we are going to do.
We must work out how to enter the scene without damaging or destroying any evidence.
Normally we then send someone in to look over the scene initially to report back to the other.
We then set out some working hypotheses taking into account all the possibilities as to what has happened.
We identify likely contact points where a suspect is likely to have left the most evidence.
We record the scene using photographs, sketches, videos and sometimes make audio commentaries where we describe what we see. We must be very careful not to destroy, contaminate or miss any important evidence that might be present. we always wear protective clothing – you know the white suits you see on the t.v and normally masks gloves lights and hardhats (if you investigate fires like me)
sometimes we will interpret evidence at the scene but it is very common to recover evidence at take it back to the lab for testing. How we recover this evidence depends on what type of evidence it is. maybe the other scientists can tell you more about this. the most important things about the evidence you take ids that it has to be packaged to protect it form being damaged or changed and to protect us from it. it must also have a detailed label and we must sign the labels and everyone who handles it must do the same. this last part is called continuity or chain of evidence. this must be kept all the way from the crime scene until the evidence is shown in court.these are the main principles of going to a crime scene. I hope that answers part of your question. If not let me know.
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Sue Carney answered on 17 Jun 2011:
Hi jonybraly. Great question!
Craig’s given a fantastic answer on what happens at the scene. I’ll try to explain what happens next in the sort of cases I deal with:
Items recovered from the scene are sometimes brought into the lab by police officers, especially if it’s a very serious case like a murder. However, for most cases each police force usually has a regular delivery of items which go to the usual forensic lab that they use. When the items arrive at the lab they are all packaged up, as Craig has already mentioned, and come with paperwork that the police officer investigating the case has filled in. The paperwork tells us what the incident was and gives a list of all the items. The person receiving the exhibits at the lab checks them against the paperwork to make sure that we’ve received the right items for that case and that nothing is missing. This record, we call it the ‘receipt of items’, can be used in evidence later on in the case, so it’s very important that it’s correct. The items are then usually recorded on an electronic system, put into storage (either a secure dry room or secure freezers, depending on the item) and the paperwork is put into a case file.
When a scientist like me receives the case file, I read about what happened in the incident and usually telephone the investigating officer to ask a few questions, to explain the tests that we’re going to do and to discuss my expectations of what the results might be and some of the limitations of the work we’re about to do. In devising my strategy, I’ll usually summarize the case information, including the answers to any questions I’ve asked the officer, and write down the specific issues that the scientific tests are going to try to address. In thinking about the strategy, it’s important to consider what the alleged incident was, and if there’s a suspect, then I need to also think about the suspect’s version of events. The strategy includes my thoughts on what the results of the tests would be if the incident happened versus what the test results would be if the suspect’s version of events happened. If I’d expect to get the same result, regardless of which version of events were true, then it might not be worth carrying out that particular test because the result wouldn’t help to differentiate between one version of events over the other.
When the forensic strategy is done, I write down a set of instructions to say which tests need to be done on which items. One of my forensic examiner colleagues then takes the instructions, gets the items out of storage and carries out the tests. At this point, they check that the packaging containing the item is still secure, so we can say that there’s no chance that the exhibit has been contaminated. They also record the details of which room and which bench they examine the item on, to maintain the ongoing record of everywhere each item goes to and who had contact with it. Sometimes I do some of the tests myself, but usually, the examiner calls me and I go to the lab and look at the items at various crucial points during an examination. We call these ‘critical findings checks.’ In most body fluids cases, these might include looking at the result of a chemical test, or looking at a blood pattern to make an interpretation of how it might have been caused. It’s usually during these checks that I discuss with the examiner which body fluid stains we’re going to DNA test. Some items might have lots of stains on them, and it’s not practical to test them all, so it’s very important to pick the ones that will give us the most information to interpret later.
When the lab work is done, the examiner puts a set of case notes about each item into the case file, and I later add the DNA results from the stains we tested. I go on to interpret these and write a statement which explains what was alleged to have happened in the case, what the suspect said, which items we received at the lab and when, what the purpose of the examination was (as written out in my strategy), what we examined, what the results of the tests were and finally an interpretation and conclusion which explain what the scientific evidence means and whether it supports the allegation or the suspect’s version. When my statement is complete, another scientist checks it and we often have lots of discussion about how I’ve explained the interpretation, to make sure it’s clear and easy to understand. When writing a statement, it’s important to remember that the people who are going to read it are not scientists. This ‘peer review’ is the final procedure before I send a signed copy of my statement to the investigating police officer in the case.
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Richard Case answered on 17 Jun 2011:
Hi Jonybraly,
Craig and Sue have given you excellent text book answers, but I have a few things to add.
What do you mean by a simple forensic crime investigation? I have 2 interpretations on this:
A simple investigation could be the investigation of a non-serious crime… don’t get me wrong all crime is serious, but there are only certain offences where they secure the scene with the yellow tape you see on tv shows and wear the head-to-foot white suits you see on the news. On run-of-the-mill burglaries and car crime, CSI’s will only look for key pieces of evidence at places at the scene where the suspect has been. These key pieces of evidence are fingerprints, DNA and footwear. Footwear is shoeprints.
Another meaning of simple is if the person(s) committing the crime doesn’t care whether they leave forensic evidence or not. Therefore they leave evidence everywhere. If you are lucky enough to encounter this type of scene then you will want prioritise what evidence to recover.
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Shane Pennington-Cooper answered on 20 Jun 2011:
Hi Jonybraly.
Unfortunately there is very little I can add, Craig, Sue and Richard have basically covered it all, however I would never say there is ever a simple forensic crime investigation, it was simple their would not need a forensic scientist (such as a theft from a shop that was manned). I will let Anna talk about the Anthropology side of things so I will briefly describe what an entomologist would do. An entomologist (person who studies insects, arachnids [Spiders] and chilopods [centipedes]) would collect any evidence ranging from insect faeces (poo), dead insects, maggots, live insects and any evidence which shows insect activity. This evidence is then taken back to the lab and predominantly used to estimate the time of death. An entomologist would look at the stage of the maggot for example, maggots go through different instars (stages), each stage has a different length which can be referenced with known samples. To determine the species of fly for example we rear a few of these maggots to imago or adult stage which we can then identify. Based on the stage of the maggot we can determine that the egg was laid say between 18:00-20:00, it takes around 12 hours for the egg to hatch and reach its 3rd stage, from this would could then estimate time of death to around 06:00-08:00 am. (Figures are simply examples and should not be used as a reference)
Hope this answers your question.
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Anna Williams answered on 21 Jun 2011:
Hi Jonybraly,
Well, the others have given excellent answers, so there’s not much I can add, except from the anthropologist’s point of view. I’m not quite sure what you mean by ‘simple’, as I don’t think any forensic investigation is simple, but it could be quite straightforward, especially if it is skeletal remains and not a fleshed body.
In a “straightforward” case, the police would bring some bones into the lab, or book some time in the morgue, where I would do my investigation. As Richard has said, these ‘exhibits’ would all be clearly labelled and documented and there would be a clear ‘chain of custody’. I would have to sign to say that I had received the bones, and they were now in my custody.
I would be wearing personal protective equipment, and I would take the bones carefully out of the body bag or evidence bag that they’d come in, and lay them out on the guerney. Hopefully, pretty soon I would be able to tell the police officers if the bones were animal or human (once you have a bit of experience, you can tell quite quickly, if there is enough of the bone present). If they are animal, then the police say thank you, and go away, leaving me with the bones to keep for my reference collection, and usually, the case is closed, because there is not a murder of a human being.
If the bones are human, then I will tell the police some initial findings, while they are standing there. I may be able to say ‘child’ or ‘female’ or ‘male’ or ‘old adult’, but usually nothing more until I have had a good look at the bones. The police officers will then leave me to get on with the analysis.What I do is carefully lay out the bones in anatomical order – ie the correct order that they are in the body – skull, then vertebrae (spine bones), then ribs, etc. This enables me to see very quickly if there are any repeats of bones – ie if there could be more than one person represented, and if there is anything missing that the police should send a SOCO or an archaeologist out to look for.
1. Firstly, I start on trying to work out the sex of the skeleton. I only do this if it is clearly an adult skeleton. In children it is very difficult to work out the sex before puberty. I look at the skull and the pelvis for certain features that are more common in men or women, and look for the features in the pelvis that allow for childbirth. In the skull, I am looking for rugged features, like prominent eyebrow ridges, or the bump at the back of the ear, or the one at the back centre of the skull, where the neck muscles attach. I also measure the diameters of the balls of the ball and socket joints such as the hips and the shoulder, which can give a good indicition of sex.
2. Then I look at age. If the skeleton is an adult (what I’m sticking to here), then I’m looking for signs of wear and tear in their joints, and the joints of the pelvis in particular. There is good reference material which shows pictures of the joint surfaces of people of known age, so it is easy to compare the joint surfaces with these pictures. I also look at how fused the bones of the skull are, as this is an indicator of age, and how worn the teeth are. I also look for signs of disease associated with ageing, for example arthritis, and I look for cartilage that has turned into bone, which is a sign of ageing. The older someone is, the less accurate I can be with the age estimate.
3. I also try and estimate how tall the person was before they died. I take simple measurements of the long bones in the leg (if the legs are present), and put them into some equations which give us a height range.
4. I can also try to give the police an idea of where this person came from – ie their ethnic ancestry. I look at features of their facial skeleton, such as the shape of the eye sockets, the protrusion of the cheekbones and teeth and the shape of the teeth. Some features are characteristic of certain populations around the world, so I can maybe make some inferences about their genetic makeup.
5. I also look to see if there are any signs of disease or old fractures that might help the police when looking for medical records to compare to the skeleton. I can say if someone perhaps walked with a limp, or had a finger missing, or had scars on their face due to a disease that affected their bone.
6. I also look for signs of trauma that are ‘consistent with’ death, or ‘incompatible with life’, which means the person is likely to have died from it – for example, a blunt force trauma blow to the head. If this was the case, I would try to reconstruct the skull, and work out how many times the person was hit on the skull, and from which direction, by looking at the fracture lines. I would also look for ‘defence wounds’ on their hands if they were trying to protect their head by covering it with their hands.
7. I also look at the teeth and try to see if there’s anything unusual that might mean the person could be identified by dental records. I get a forensic odontologist (dentist) in to help me.
When I have done all that, i write up a report for the police with my findings and conclusions. I send my report off to another local forensic anthropologist to check that I haven’t made any mistakes and that my conclusions about age, sex etc are correct. Then I wait to see if I am needed to defend my evidence in court. Luckily, so far, I haven’t been challenged on my findings to have to go to court yet.
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