Interactive Investigator

Physical Evidence:

Hair

Fibre

Footprints

Scratch mark

Letter

Fingerprint

Blood stain

Wound

Paint chips

Fields:

Pathology

Forensic Sciences

Coroner

Ballistic

Uses of evidence:

Footwear impressions allow you to match the impression with actual footwear owned by suspect.

Toolmark impressions allow you to match the impression with actual tools owned by suspect.

Paint examination allows you to match a tool to the crime scene, when the tool is found.

Computer composites can help with suspect identification.

Hair analysis enables comparisons with the suspect's hair or with hair found on the suspect's clothing

Document analysis can verify the authenticity of a document and who the author is.

Fingerprint analysis is still the predominant means of establishing positive identification.

Fiber analysis rests on the principle that whenever two individuals are in contact, materials (dust, paint, cloth...) are exchanged at a microscopic level.

Blood stain pattern analysis tells you how a crime was committed.

Blood analysis lets you identify a victim or a suspect, because DNA is unique to each individual.

Wound analysis can help with identifying the murder weapon.

Pathology allows you to establish time of death and compare with suspect's schedule.

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Evidence found

Place of entry:

Footwear impression:

- photographed with and without a ruler, taken from all sides

- castings made

- footwear acquires individuality as it is worn down --> defects such as cuts and abrasions occur

- footprint left behind was worn at the heel --> suggesting that the suspect drags his feet

What to do with information:

When a suspect is found, his/her home and/or place of employment should be searched in order to find boots that match the impression at the lab.

Lock on back door was forced open by a tool:

- someone was determined to get inside

Since entire door cannot be removed,

- photographs taken

- silicone impressions of the grooves left by the tool used are made

- identify tool by comparing tools and other marked objects

3 types of tool mark impressions:

Compression: tool surface presses into a softer material

Sliding: tool scrapes across a surface causing parallel striations

Cutting: combination of compressing and sliding

Mark impressions left by tool used by suspect:

Compression: tool made slight indentation in wood

Sliding: in the metal surrounding impression

Tool used --> crowbar

What to do with information:

Search all suspects' homes in order to find a match for the tool.

Paint chips:

- Often found when a tool is used on a painted surface

- Minute traces of the paint, when the tool is found, can be matched to the crime scene.

- Minute traces may also be found on a suspect's clothes or person.

- Matching is done using the concepts of class and individual characteristics. This methodology also applies with incidents involving motor vehicles.

How to collect evidence: holding a paper bindle open and scraping chips into it with a clean knife type blade

What to do with information:

Look for minute traces of this same paint on the tool used to break into the house (if it is found) or on the suspect's clothes.

Imagery and Computer Composite:

If there is a witness to the suspect, the witness will be asked to describe as much as possible about the suspect. A forensic artist will then do a composite drawing of the suspect either

- manually

- using a computer imagery

- both

Computer imagery:

- Database of many styles of facial features available

- Showing them to a witness enables the witness to come up with a clear image.

- The artist also notes height, weight, hair colour, eye colour, gender, race, and age of the suspect.

- The artist's success comes from listening very carefully to the witness.

- With a composite drawing, the Police have a much better chance of finding a suspect.

What to do with information:

Use these sketches to see if anyone recognizes who these women are and thus give them an identity.

Place of struggle:

Living room: Struggle between suspect and victim

Hair:

Can tell:

- race

- if the person has any drugs, poisons, or diseases in their system

- can ultimately be matched to a suspect

Why can these factors be revealed?

Hair contains DNA, and DNA encodes information that determines a person's genetic makeup. The reason hair can tell the forensic specialist what race a person belongs to, for example, is because all people within a particular race have a similar DNA code sequence, as everyone who has brown hair has a similar code sequence for brown hair. The coding sequences, however, are separated by 'junk' DNA. This 'junk' DNA is non-coding and separates coding sequences. The 'junk' DNA sequences are random and unique to each person. This is why hair can identify its owner.

What to do with this information:

If the woman with the red hair is found, and becomes a suspect for the murder, the investigators should get a warrant allowing them to obtain a DNA sample from her. The sample will then be compared to those found at the crime scene.

Document Analysis:

How documents at a crime scene are collected:

They are placed in cellophane or plastic envelopes, and are never marked, defaced, altered, or folded. At the lab, they analyze the paper, ink, and handwriting.

Questioned documents:

Forensic Science disciplines:

- paper and inks

- handwriting analysis

- writing instruments

- typewriting

- photocopying

- computer printers

- computer disks

- forgery

- gambling machinery

- rubber stamps

- dating of documents

Handwriting analysis:

Examines -

- design

- shape

- structure

to determine authorship

Graphology - not a forensic science but a study of a person's handwriting to determine their personality traits

What to do with this information:

Go to the shop (that the paper was sold at) and ask if any of the sales clerks recognize the sketches of the two women who were seen at the victim's house on the day of the murder.

Fiber Analyis:

"Locard's Exchange Principle": when someone comes in contact with another person or place, something of that person is left behind, and something is taken away.

It utilizes the concepts of class and individual characteristics, thereby determining the type and colour of the fibre.

What to do with this information:

When a suspect is arrested, their home should be searched to find a garment with fibers that match the fiber in the police's possession.

Place of murder:

Bloodstain Pattern Analysis:

Blood reacts, as all liquids do, in a predictable, consistent, reproducible manner. The types of reactions are called 'standards'. These standards can tell the expert how a crime was committed by the stain the blood leaves.

Different splatters occur, for example, when blood falls from different heights.

When there is a blunt force trauma, and blood splatters, the stains left are called 'cast off stains'. Cast off stains reveal:

- direction and number of blows

- size of the object used

- orientation of the person

- if they are right or left handed

Body of victim:

2 puncture wounds:

- Neck

- Heart

--> shows that attacker is experienced and has been in many fights to be able to know where to stab

Splatters on wall:

Suspect stabbed victim in the neck --> hit carotid artery --> blood comes out in spurts --> great loss of blood occurs within only a few seconds if it is a major artery --> victim lost consciousness quickly --> could not defend himself against second attack when suspect aimed for the heart --> victim fell where he stood --> died almost instantly

Direction: lunged forward at victim using a downward motion --> attacker must be at least as tall as victim

Bloodstains:

Neck - accounted for most of the large bloodstain that seeped under the body

Heart - murder weapon nowhere to be found --> suspect pulled knife out from the victim's heart --> heart bled a little --> would have almost no blood if the knife was left in --> because knife would have acted as a plug

What to do with this information:

When a suspect is arrested, they should take into consideration that he or she has to be at least 5'9" tall and with either a criminal record or a self-defence background (such as Martial Arts or military training).

Wound Analysis:

2 puncture wounds made with a switchblade (small pocket-knife)

Nature of wounds indicate that the blade was:

- narrow

- approx. 4 inches in length

- good quality,

blade did not break when victim was stabbed

---> not easy to stab someone in the heart --> must get past thoracic cage which is designed to protect vital organs --> blade went all the way through + tip did not even break --> good quality switch blade

What to do with this information:

When a suspect is found, his/her home and/or place of employment should be searched to find the same type of weapon.

Blood Analysis:

Blood found at a crime scene can tell through chemical analysis if the personhas any drugs or poisons in his or her system. Through DNA analysis a person's genetic make up may be identified. A very important use of DNA typing is the identification of perpetrators of a crime by comparison of biological samples of suspects against biological specimens that the perpetrator of a crime has directly left at the crime scene (e.g. semen, saliva, skin, or blood). The reason blood can tell the forensic specialist what race a person belongs to, for example, is because all people within a particular race have a similar DNA code sequence, as everyone who has brown hair has a similar code sequence for brown hair. The coding sequences, however, are separated by 'junk' DNA. This 'junk' DNA is non-coding and separates coding sequences. The 'junk' DNA sequences are random and unique to each person. This is why blood samples can identify or eliminate a suspect.

What to do with this information: When a suspect is arrested, a blood test may be performed in order to find a DNA match between the suspect's blood and the blood found at the crime scene.

Time of Death:

Tells us what time victim died

Factors considered:

1. Livor mortis (can also show if the body was moved)

Setting of blood in the dependant regions of the body following death

e.g. blood has accumulated in the back of the body

shows that:

- after vicim died, he was lying on his back for several hours

- was not moved after he was killed

2. Rigor mortis

Chemical reaction that causes rigidity in the muscle groups following death.

After half an hour

Muscles go stiff, but then they go limp again

Only after about 12 hours

Body becomes very stiff

3. Algor mortis

Cooling of the body

What to do with this information: Ask the different suspects where they were at the time of the murder, and if anyone can confirm their alibi.