Unit 4 - Forensic Investigation Procedures in Practice
All documents for this subject (38)
Seller
Follow
abaish05
Reviews received
Content preview
Unit 4 Assignment B
Aimee Baish FSC year 1
Types of tests in forensics
There are physical tests like footprint casting, toolmark analysis, ballistics analysis, document
analysis, fibre analysis, and digital evidence analysis. There are also biological tests which are
identification tests, presumptive tests, DNA analysis and confirmatory tests. Identification tests are
tests used to figure out what a substance or material is. They are also used to tell if blood or bodily
fluids comes from a human or an animal, they can also show where the blood came from (hand, leg,
face, menstrual blood, etc.). Identification tests also individualise blood or bodily fluids.
Individualisation is where blood and bodily fluids can be revealed to have come from one person or
animal. Presumptive tests are tests where we analyse a sample and then it tells us whether the
sample is one thing or another, for example if hair and blood is human or animal. Confirmatory tests
(diagnostic tests) are used to confirm that the presumptive test was correct. The chemical tests used
are chromatography, the marquis test (a chemical presumptive test), mass spectrometry, the
cyanoacrylate method (the superglue fuming method) (a chemical enhancement test) and
spectroscopy (colorimetry, infrared and ultra-violet).
Footprint casting is where a footprint indent gets filled with a plaster mixture, and then when set,
you would have a cast of the footprint. However, if the footprint has been left on sand, then
footprint lifting techniques are where you use a gel or an electro-static device to lift the footprint if it
couldn’t be casted. This technique would still give you a physical version of the footprint, it just
wouldn’t be like a plaster casted version. Before casting or lifting a footprint, you should take
pictures of it with a scale next to it to show how big the size of the print is. Preferably in a 1:1 scale
to the actual size of the footprint. Footprint analysis is where a footprint is looked at either by a cast
or a lift of the print. But a lot of the time footprints are analysed on photographs instead. But either
way to analyse a footprint you must look at the patterns and the size of the footprint, as well as the
width of the footprint. These features make it easier for us to distinguish certain characteristics of
the shoe wearer. Footprint analysis is good for putting a certain person in the crime scene; however,
it isn’t fool proof and can go wrong. As all the analysis does is tell you which kind of shoe it is, what
brand of shoe it is, the approximate height and weight of the wearer, the shoe size of the wearer,
maybe the wearers hobbies and how the wearer walks, due to wear patterns. Footprints are one of
the most common pieces of evidence that are left behind at a crime scene. However, that doesn’t
mean that they are definitive evidence, because many people have the same shoes and shoe size
but both people walk differently until you look at the identifying factors of the footprint you
wouldn’t see the difference in the two footprints. Due to class characteristics, which are the
characteristics that every shoe of the same brand and model have, and the identifying
characteristics are the thing that are specific to that person’s foot, like wear marks from walking a
certain way.
To analyse a toolmark, you must look at what has been left at the scene by the tool, the size and
shape of the mark on the surface that the tool encountered. Then to determine which tool and
brand it came from, you must take pictures of the mark/dent with a scale next to it, and maybe even
on a 1:1 scale, as this shows the true size of the mark. You can also make a silicon cast of the
mark/dent, and you could even do a re-enactment of the dent/mark with different tools until you
get a physical match of the mark/dent compared with the one from the scene. Then when you have
found your results, you write your findings in a clear report format and then state whether or not it
is possible that the unknown tool was or was not at the scene and caused that mark/dent.
, Ballistics is the field of investigation which includes: the angle of trajectory that a bullet travelled at
after being fired from the firearm, the marks on the bullet made by the barrel of the firearm and the
harm that a bullet caused/causes when it hits a surface. Every firearm has a different barrel which
leaves different marks on the bullets it fires, so when a bullet or its casing is found you can analyse
the marks on it and the size of the bullet to distinguish which gun it came from. The bullet looks like
every other bullet until it has been fired. Ballistics analysis is taking the bullet casing and looking at
the markings which were left by the marks in the firearm barrel. So, when the bullet is found they
can trace which gun it comes from. This is called a ballistics fingerprint. You can also perform a
trajectory analysis which is figuring out what trajectory the bullet was fired from, and then where
the bullet was shot from by looking at the trajectory that was the bullet was found to travel at and
comparing to the trajectory that it would have travelled from at different places around the scene.
Another way to find which firearm the bullet came from is to compare the bullet(s) and the cartridge
case(s) under a split screen microscope, which would lead to finding the bullet came from that
cartridge case or another one. A split screen microscope is a microscope where there are two stages
and bases, but there is only one eyepiece, so the images from both stages would show up next to
each other.
Lots of different types of documents can be found at a crime scene, like your different forms of ID
(provisional or driving license, passport, or other ID cards), bank statements, your will, any contracts,
stamps, handwritten letters, and even your electronic documents. The most common way to analyse
these is to use the light or electrostatic techniques rather than the techniques that could end up
with the document getting destroyed. Document Analysis is when you are looking at documents for
any changes. You can use ninhydrin to find fingerprints on the paper. You can also do analysis on ink,
so that you can see under scribbles, and so that you can tell the difference between inks and if they
used a different pen. You can use microscopy to see changes in handwriting or see the fingerprints
after ninhydrin. You can also use infrared and ultraviolet lights to look for any hidden messages or to
look for things that aren’t visible to the regular human eye. Using this would mean that if the ink a
message was written in was a more purple or blue toned black pen but then was covered up by
someone else who used a more red-toned black pen then if you shine a UV light over the paper and
then put on an infrared filter, you’ll be able to get rid of the scribble that was over the top of the
message. Using digital imaging instrumentation is where a machine is on top of your work top, and
your place the document under the machine, and it detects the writing on documents, so like writing
on your digital documents, it will read into the code and find out is the document is forged, or edited
by someone else, that isn’t the owner. Electrostatic Detection devices (EDDs) are used for findings
indented writing, for example the writing under a scribble, like a mistake. Analytical chemistry, more
specifically, liquid chromatography is also used to analyse documents. It’s used to analyse the ink on
a document. Normally there will be two samples taken from the paper and then both samples will
be put into columns, and then put into a machine which produces the chromatogram, to show you
which substances are in the samples.
Fibre analysis is a presumptive test and a confirmatory test, which determines and investigates
fibres. Fibre analysis can be used at macro and nano level. Fibres analysis can create a link or a
separation between a suspect and the scene, as the fibres could be from the suspects clothes but
when we know they are or aren’t we can say whether the suspect was or wasn’t at the scene. Fibre
analysis is where you look down the microscope at a fibre and then try to determine which type of
fibre it is based on how the sheath of the fibre looks. Fibre analysis can be done using many types of
microscopes, optical light microscopes, scanning electron microscopes (SEM) and transmission
electron microscopes (TEM). Optical light microscopes are the most common type of microscope, as
they are the smallest and cheapest. They work by using a light to illuminate the stage with the slide
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller abaish05. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.18. You're not tied to anything after your purchase.
