DNA Testing

I had deputy J. Gale make notes of the crime scene. I had him include a log that records the time of discovery of the crime, the identity of the person who reported it. I asked him to include observations and descriptions provided by other people at the crime scene, the date and time photographs are taken, the name of the person who discovers each piece of physical, its description, location, and the name of the person packaging and marking of the evidence. These notes could be used to refresh someone’s memory of the crime, so I told deputy J. Gale to use lots of detail. I thought about the use of videotape but it would still have o be transcribed into written document which is time consuming.

Fingerprints When we began searching for the fingerprints the first place I thought would be most appropriate would be where the crime actually took place. I begin my search at the window. I found a partial print on the window. I had the print photographed and then had it lifted using a special transparent tape then protected it with a stiff, transparent cover. The next object that I tested for fingerprints was the drinks can. I had to use the Reflected Ultra Violet Light Imaging System (RUVLIS) to try to reveal any latent fingerprints.

One full print was found on the drinks can. I had the print photographed. To develop the print I had to use cyanoacrylate vapour (super glue) in conjunction with sodium hydroxide in the lab. The fuming process is carried out in an airtight tank. Once the ridges have been hardened it is treated with a Dye, this makes it fluoresce under laser illumination. The same process is used when testing for fingerprints on the empty bottle.

When it came to testing for prints on the brick I used a chemical called Ninhydrin. I sprayed this chemical over the surface of the brick. Any prints present on the brick will then turn a blue/purple colour when they are developed. The reason why we collect fingerprints is to find out who committed the crime. We can only convict someone if we have their fingerprints and DNA on file. We usually only have criminals fingerprints on file. When we want to search for a fingerprint match, we cannot just search through the whole system, this would normally take days to search through whole system.

To narrow down the search we look at the ridges on the fingerprint, when comparing fingerprints, people of the same race had similar characteristics, so we are then able to decide race a person is by comparing it to fingerprints on our database. Every person has a unique fingerprint, so fingerprints are extremely strong evidence when presented in court. With the prints that we found we should be able to narrow down to a curtain race.

DNA Testing

The next object I tested was the drinks can, I was testing the saliva residue that was left behind by the person drinking from the can. To test the saliva for the DNA I used a process called polymerase chain reaction (PCR). I used this type of DNA testing as it can test the smallest amount of DNA by amplifying the DNA. There is a small problem when using this DNA testing, if another piece of DNA contaminates the DNA that will also be contaminated. I also used the same process when testing for DNA on the cigarette butts. The reason why we do DNA testing is to find the criminal of the crime, even if you have not got the DNA of the person on file it can still tell you quite a few other things. DNA can tell you the gender of the person, whether they have any diseases, eye colour and hair colour. No one has unique DNA except for identical twins. The only way to tell twins apart I by their fingerprints.

Collecting Evidence When it came to collecting evidence I made sure that all evidence was marked for identification and logged. All objects of a cubic inch or larger should be inscribed with the investigators initials but scribed away from any potential evidence traces. Marked and unmarked items are further protected by put in sealed containers in which the seal has to be broken to open. The investigators name or initials are then written on the seal with the date. An adhesive label is then fixed to the box or envelope bearing case information as followed:

I assigned deputy S. Edmonds for the collection of evidence to be sent back to the lab for testing. I made sure that the samples being tested for accelerant were packaged in airtight nylon bags that are goose necked, this is so that evaporation of the substance would not take place. The empty bottle was tested for accelerant and then samples from the room were tested. The test used to identify if an accelerant was used and what type of accelerant by the process of gas chromatography.

Foot Print The foot print left behind in the soil, we were able to make a cast of it. We firstly had to spray it with a clear acrylic lacquer, this hardens the print, dental stone is then poured in and sets quickly. The reason why we do foot print casts is so that we can then find the size of the shoe, the manufacture of the shoe by comparing it to a database of shoe prints. With these we are then able to prove who was at the scene of the crime by comparing it to different shoes.

Glass The next thing we collected was glass samples from the inside of the staff room and the window itself. We then tested the glass to see if the light rays refract the same way to find out which direction the window was smashed, we then tested to find out if the glass had the same respective densities, this is done by dropping two samples of glass into two containers with the same liquid, if the glass are suspended at the same level then they have the same densities.

The reason why we did this test was because we wanted to find out whether the glass was smashed from the outside inwards or the other way round and whether the glass on the inside of the room matched the window and that it did not come from a different source such as a glass bottle. Trace evidence A flower Bush is located outside the staff room window. I notice that a few of the branches have been broken. I take a sample of the pollen found on the bush as some may have been transferred to the clothes of the person who broke the branches. The reason why we did this test was because if we found that this pollen was present on a persons clothing then we could prove that they were present at the scene of the crime.

Exit point The foot print leads away from the scene, maybe the exit of the scene but also the entrance. There are indents in the grass which leads to the perimeter fence. There is no way under the fence and a piece of fibre on spikes on the fence. This fabric can then be compared to a piece of clothing from a suspect. We know the direction they left so we can perform a search in case they dropped anything in a hurry. A thorough search of the entire staff room is made to try to find the incendiary device, it my have been destroyed by fire, the flash over.

The wiring in the staff room is checked to eliminate possibility of an electrical fire. I asked the staff who were in that room during the day the day, if there were any alcohol or flammable substances in the staff room at the time. The questions that I asked the staff were; Did the teachers know of any student that had a reason to destroy the coursework? The teachers did not now of anyone at the time who would want to destroy the coursework. Did they know of any student that cheated on their coursework? They did not know of any student to have cheated on their coursework.

Was there any student that was expelled recently? There was two students that were expelled recently for trying to break into the school for some reason. We did obtain the CCTV camera tape of the day. The angle of the camera allows very limited vision, one person is visible on the camera 15 minutes before the fire took place. He appeared to be leave before the fire took place. He was interviewed, he said he was having a cigarette, his DNA matches the DNA found on cigarette butts, but his prints did not match that on the empty bottle or the saliva on the drinks can. I had deputy S. Edmonds take a sample of the soil by the footprint for testing a later comparison if needed.

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