Transcript CSI – Collecting Evidence

CSI – Collecting
Evidence
Forensics
Forensics = the application of science
to law. Forensic science is used to
investigate criminal cases involving a
victim, such as assault, robbery,
kidnapping, rape, murder and civil
cases such as forgeries, fraud, or
negligence.
 Used in court of law, involved
application of science to legal problems

I.D. of a Firearm &
Ballistics (travel of bullet
until impact)


When a criminal fires a gun, clues will be left. A
bullet from a spent cartridge can be traced to a
gun. This is possible because of the basic design
of a firearm
When bullet is fired and travels through barrel =
rifling cuts mark into the bullet – these grooved
markings are called STRIATIONS and each gun
will have different striations which means police
can tell what kind of gun was used in a crime if
they find a bullet
I.D. of a Firearm &
Ballistics (travel of bullet
until impact)



When they find a weapon, lab technicians will
fire test bullets into a cotton wall or water tank
to check power and accuracy
Ballistic science can also determine whether or
not a person was holding a gun when it was
fired
Ballistics can also determine the
TRAJECTORIES = path of the bullet
Forensic Entomology





Study of insects to a legal investigation
Insects of interest to because they eat dead
matter – including humans
Because they have set living and reproductive
cycles, insects can be used to establish how long
a corpse has been dead and if it has been moved
They arrive soon after death and they are cold
blooded so they are attracted to the body
Sometimes the movement of suspects, goods
and vehicles can also be traced via bugs
Forensic Toxicology






Toxicology is the study of substances which are
harmful to human beings
They have the responsibility of detecting and
identifying the presence of drugs, alcohol and
poisons in fluids, tissues, and organs (i.e., rat
poison under the sink)
The work of a toxicologist falls into 3 main
categories
Testing for alcohol in blood or urine
Identification of drugs such as heroin, cocaine,
cannabis etc.
Detection and I.D. of drugs and poisons in body
fluids, tissues and organs
Forensic Toxicology





Sample types:
Urine: quick and easy for a live subject, and is common
among drug testing for employees and athletes
Blood: sample of choice for measuring blood alcohol
content in drunk driving cases
Hair sample: hair is capable of recording medium to
long-term or high dosage substance abuse. Chemical
in the bloodstream may be transferred to the growing
hair and stored in the follicle
Other: samples collected during an autopsy. I.e.,
stomach contents to detect undigested pills or other
common organs such as: eye, brain, liver or spleen
Handwriting & Ink
Analysis




In cases ranging from ransom notes and death threats, to
forged cheques and wills, the forensic document examiner
is called in to examine handwriting
Want to look at NATURAL STANDARDS = normal
written material i.e. love letters, cheques, shopping lists
Want to look at REQUESTED STANDARDS = request
person to write them on the spot – problem here is they
may try to alter writing
Also test ink to determine the age of the ink, type of ink,
whether ink has been removed from a document. I.e.
works well for historical documents that have been forged
DNA


Last decade DNA has taken huge steps for law
enforcement – many feel it’s the greatest
advance in forensic science since the intro of
fingerprints a century ago
To use DNA technology some biological matter
must be found i.e. saliva, blood, semen, vomit,
hair + any other fluid – only need a sample the
size of a pin prick and can do DNA testing on
saliva from a dried cup, a smoked cigareete or a
licked stamp
Other traces

Hairs – people lose a minimum of
about 100 head hairs every day –
during a crime they can be shed or
pulled out
Blood Pattern Analysis
(BPA)








Can look at blood stains at a crime scene and
determine:
Type of death i.e. gunshot, stabbing
Where victim was prior and after event
Type of weapon used
Amount of force used by offender
How long ago the crime took place
If offender was right or left handed
Whether they may be blood on the assailant
Footprints



Shoe marks are the second most common type of
evidence found by the police after DNA, and unique
patterns of wear and scuffing make it possible to match a
mark to an individual shoe.
Footwear marks were found at around 40% of crime
scenes. It is even possible to recover a shoe impression
from a carpet or a dead body.
But although a footmark can show that a criminal had
visited a burgled house, for example, it would almost
always be used with other evidence. It can also give hints
towards a person’s height and the manner in which they
walk. I.e. limp, walk over.