CSI Lesson 4

We did a flame test!

1. How and what is a flame test used for in "crime scene investigations/forensic science"?
2. If there are more than one trace metal present, is it the flame test still suitable technique to identify the trace metals?
3. Is flame test sufficient to identify the trace metal(s) present?
4. What is "Mass Spectrometer"?

Answer Q1: It is used to separate and identify the componential elements in a sample from a crime scene. Different metals change the colour of the flame when they are heated. Flame tests are based on the physical and chemical principle that atoms return to their normal energy state by giving off excess energy in the form of light when heated by a flame. Each element has its own characteristic light frequency. In this way, flame tests help to identify essential elements present at a crime scene and hence, narrow down the search for the perpetrator.

Answer Q2: No. More than one trace metal would result in a flame comprising of a mixture of colours, making it difficult to identify the various trace metals involved.

Answer Q3: No. The test cannot differentiate between all elements as some produce the same flame colour while others do not change the flame colour. Also, impurities or contaminants can affect the test results. For example, Sodium is present in most compounds and could influence the colour of the flame.

Answer Q4: It is an instrument that can measure the masses and relative concentrations of atoms and molecules by making use of the basic magnetic force on a moving, charged particle.

CSI Lesson 5 (28/7)

Today, we did paper chromatography!

Partner: Crisann Moh (4)

However, our results were really faint. A possible reason is that we diluted the ink too much.

3rd CSI lesson (21/7/11)

3 main fingerprint patterns

- Arch (0 delta)

- Loop (1 delta)

- Ulnar loop: ridges slope towards little finger

- Radial loop: Ridges slope towards thumb

- Whorl (2 deltas)

3 types of fingerprints can be found at a crime scene

Patent (e.g. Visible prints when fingers have blood on them)

Plastic (e.g. Indentations made in soft like material clay)

Latent

Methods of Lifting Fingerprints

- Super glue fumes

- Dusting powder (readily adhere to perspiration residues and/or deposits of body oils left on the surface)

- Silver nitrate spray (reacts with chloride in the salty sweat to show a print)

1st principle: Fingerprint is an individual characteristic

- No 2 individuals have yet been found to possess identical ridge characteristics

2nd principle: A fingerprint will remain unchanged

- It is unchanged during an individual's lifetime
- Even after injuries and burns the same patterns will return as the skin heals

3rd principle: Fingerprints have general ridge patterns

Observations:

• Compare the fingerprint patterns on your right and left hand. Are they mirror images of each other?

No.

• What kind of patterns do you see?

The thumb of my right hand is in a whorl pattern whereas the thumb on my left is in a radial loop pattern.

• Do the loops curve in the same or different directions in different fingers?

Different directions.

• Compare the size of the patterns eg. How many ridges make up a loop?

3rd CSI lesson

Class	Class Index Number	Your fingerprint pattern
210	9	loops
210	4	loops
210	10	loops
210	2	arches
210	24	whorls
210	28	whorls
210	27	whorls
210	15	loops
210	29	loops
213	27	whorls
213	17	whorls
213	7	whorls
213	15	loops
213	20	loops
213	26	loops
213	30	loops
213	32	arches
213	25	loops
213	24	loops
213	23	arches
213	31	whorls
213	16	whorls
213	13	whorls
213	21	whorls
213	4	arches
213	29	loops
213	2	whorls
213	14	arches
213	19	arches
213	22	loops
213	6	loops
213	10	loops
213	3	loops
213	33	loops
213	18	loops
213	28	loops
210	18	whorls
210	19	loops
210	17	whorls
210	3	whorls
210	21	whorls
210	8	loops
210	25	loops
210	6	loops
210	10	whorls
210	30	loops
210	25	loops
210	1	loops
210	16	loops
210	20	whorls
210	31	whorls
210	6	loops
210	32	whorls
210	5	loops
210	13	loops
210	7	loops
210	11	whorls
210	26	loops
210	12	whorls
210	23	whorls
213	1	loops

2nd CSI lesson (19/7/11)

Ridges and pores activity
Introduction:
A friction or epidermal ridge is a raised portion of the skin on the fingers and toes. Impressions of fingerprints may be left behind on a surface by natural secretions of sweat from glands that are presnet in friction ridge skin.

WOOD GLUE method
AIM: To capture ridge and pore details of your finger using a polymer cast.

Try to take a picture of the print through the eyepiece.

Questions:

• Where are the pores found? Are they regularly spaced?

Pores are found all over our skin and are regularly-spaced across the epidermis layer.

• Are the lines of your print equally spaced thoughout?

Yes, they are equally-spaced throughout

Cyanoacrylate (Superglue) fuming method
Introduction:
The actual development of this chemical method of developing latent fingerprints is somewhat unclear as many agencies and countries claim credit for its discovery. What is generally accepted is that the method came about between 1977 and 1978. It has since been used as an effective technique in many crime laboratories throughout the world.
The basic concept behind all chemical techniques is to apply something that will chemically react with one or more of the constituent chemicals of latent fingerprints. The product of the chemical reaction will render the fingerprints visible and allow the print to be photographed so that identifications can be made.
Superglues typically contain methylcyanoacrylate or ethylcyanoacrylate. They react with traces of amino acids, fatty acids and proteins in the latent fingerprint and the moisture in the air to produce a visible, sticky white substance along the ridges of the fingerprint. The resulting image is then photographed so that comparisons can be made with other fingerprints that are collected.
To enable such a reaction to take place, the cyanoacrylate must be in its gaseous form. Hence, investigators tend to use a fume box to hold the chemicals and objects in an enclosed space. Heat is then applied to allow the superglue to vapourise. If there are any latent fingerprints on the object, the exposure and humidity in the atmosphere will be sufficient to enable the reaction to take place. The actual amount of time required for such a reaction to take place depends on several factors: concentration of cyanoacrylate fumes, humidity levels and size of fume box etc. It is often required to monitor the reaction as it is almost impossible to predict the actual amount of time required for the prints to develop.

AIM: To develop latent prints on a non-porus surface using superglue fuming method.

Questions:
If the contrast of the white print against the black background is still too faint for a good detailed photograph to be captured, what could be done to enhance the fingerprint?
I increase the amount of oil on my finger by pressing it to areas of my face such as my forehead. The sweat from sebaeceous glands on the body and oils contained in perspiration enable the fingerprints to be more distinct .


Iodine fuming method
Introduction:
The iodine fuming method has historically been recognized as one of the earliest techniques used by investigators for developing latent prints. Prior to the introduction of chemical methods such as using ninhydrin and silver nitrate, iodine fuming was a preferred and recommended method to be used on paper products.
While frequently categorised as ‘chemical technique’, the development of latent prints with iodine fumes is not a chemical process but a physical one. Chemical reactions produce new substances and will result in changes of the properties of the constituents of the latent print. Eg. Silver nitrate reacts with the chloride from sodium chloride to form a white precipitate – this creates white lines that make up the latent print.
However, in iodine fuming, natural body fats and oils in the larent print temporarily absorb the iodine vapours. This results in a change in colour, often from colourless to dark brown. This temporary change fades with time as the iodine that is absorb will eventually dissipate into the atmosphere. The colour change can be made permanent by the application of certain materials but the developed latent print can usually be photographed at the greatest inensity of colour change and then allowed to fade.
One advantage of using iodine fuming is that it is an essentially non-destructive technique. No permanent or chemical change has taken place after the print develops. The latent can therefore be further processed using other methods. Additional tests for the constituents of the latent can also be conducted after the print is developed.
AIM: To develop latent prints on a porus surface using iodine fuming method.

Questions:
What are the possible substances that may be used to render the prints more permanent?
Why does the print disappear?
Natural body fats and oils from sebaceous glands temporarily absorb the iodine vapors, resulting in a change in color, from clear to a dark brown, until the effect fades with time. The color change can be made permanent by the application of certain materials.
Powder dusting method
Introduction:
The most commonly known method for developing latent prints would probably be the powder dusting method. A variety of powders are used in dusting for prints. Many of these powders contain aluminium or carbon. The finely crushed powder is gently applied to a surface and the minutes particles of powder cling to the latent residue, making it visible. These prints are then lifted using adhesive tape. For dusting to work, the surface that is being dusted must be completely dry and relatively free of other contamination.
The principle behind dusting is simple. Oils and perspiration form the common residue on fingers that get transferred when a print is made. When the powder is applied to the surface with the print, it sticks to the oils and brings out the ridge patterns.
Dusting is ideal on wood, metal, glass, plastics and tiles. It is less than ideal on paper, cardboard and leather. Powders vary in colour, stickiness, photographic and magnetic qualities. The best colour to to use is one in shart contrast to the surface colour. For example, a white or grey powder works best on a dark surface and a black powder works best on a white or colourless surface. In multicolour situations (such as a magazine cover) it is best to use a fluorescent powder. When the dusted object is exposed to ultraviolet light, the powder will glow, making the print show up regardless of the background colour.
Aim: To develop latent prints using powder dusting method

Questions:
What is magnetic powder dusting and how does it work?

1st CSI Lesson

What did Slylock observe to help him identify the trash tosser?

- Bones

Raccoon is the culprit as cows are vegetarians (eat only grass).

Awareness test

How many tosses did I count? 13.

Did you get it correct? Yes.

Reflections

- Why did I not see the bear?

I was focussed and more concerned about counting the number of passes the white team made as I thought that was the main objective of the video. I programmed my mind to only register the actions for the white team and disregarded all else.

Suspect profile

Height : 5"9

Experienced fighter (extensive self-defence training): Ex-convict (?) Street fighter(?) Martial arts/ military training

Gender: Woman (?)

Motive: Jealousy (?)

Environmentally-conscious

Men's Size 11 Doc Martins

Electrician at Bright Lights 'R' Us

Murder weapon: Most likely a switchblade

Narrow

Good quality

Approx. 4 inches in length

Place of murder

Evidence #1: Bloodstain pattern

• Puncture wounds to the carotid artery in the neck and the heart
• Hit a major artery-->great loss of blood-->lose consciousness quickly-->cannot defend against 2nd attack
• Victim fell where he stood
• Blood under the body came from neck wound
• Pattern of spatters-->suspect lunged downwards

Evidence #2: Victim's wound

Place of struggle

Evidence #3: Document

• The victim was cheating on Woman A and she was furious with him for it (melodramatic writing)
• Average ink
• Special paper-->Made by children in 3rd World Countries-->From a shop called "We Are The World"

Evidence #4: Shattered windowpane

Evidence #5: Overturned glass of red liquid (wine?)

Place of entry

Evidence #6: Lock at the back of the house was forced open

Evidence #7: Footwear impression

Right foot of Men's Size 11 Doc Martin

Worned heel-->Drags his feet (maybe shoe is too big for the foot?)

Evidence #8: Paint chips

Evidence #9: Tool marks

Compression mark: Tool made slight indentation in the wood

Sliding impression in the metal surrounding the lock

Tool: Crowbar