Results of blood splatter experiments (6th CSI lesson cont'd)

Experiment 1

Table of results of vertical distance from which the blood droplet was dropped/cm VS. The diameter of the bloodstain/cm

Experiment 2

Table of results of angle of elevation of the surface/º VS. The length and width of the bloodstain/cm

Blood splatters

Projected bloodstains

When exposed blood source is subjected to force greater than the force of gravity.

Arterial spurt/gush

Resulting from blood exiting body under pressure from a breached artery

LARGE VOLUMES OF BLOOD (patterns created by same volume of blood,

from same source to target distance)

Projected blood (through syringe)
Spilled blood

Dripped Blood

What is shape of blood splatter?

It depends on a variety of factors, such as directionality. When a droplet of blood strikes a surface perpendicularly at 90 degrees, the resulting bloodstain will be circular. However, if it strikes the surface at an angle more or less than 90 degrees, the resulting bloodstain will be elongated or oval in shape.

Describe any other characteristic of the splatter.

What are the factors that affect the shape of the blood splatter? Name as many as possible.

Type of surface the splatter strikes, direction the blood splatter strikes the surface, angle of impact, the height the blood droplet is dropped from

Generate some hypotheses from the blood splatter patterns observed above.

The greater the height the blood droplet is dropped from, the larger the diameter of the resulting bloodstain. The greater the angle of inclination, the greater the length of the resulting bloodstain.

6th CSI Lesson

Partner: Crisann Moh (4)

Experiment 1

Resulting bloodstains (height of 10cm)
Experimental set-up
Resulting bloodstains (height of 60cm)
Resulting bloodstains (height of 100cm)
Resulting bloodstains (height of 150cm)

Height: Length 1st attempt)/ Length 2nd attempt)/ Length 3rd attempt (cm)

10cm: 0.8/0.8/0.8

30 cm: 1.1/1/1.2

60cm: 1.3/1.5/1.3

100cm: 1.8/1.8/1.9

150cm: 1.6/1.6/1.8

Experiment 2

Resulting bloodstains from the whole experiment

Angle(degrees): Length/ Width

1st 10: 1.5/1.4

2nd 10: 1.6/1.5

3rd 10: 1.7/1.6

1st 30: 1.8/1.2

2nd 30: 1.5/1.4

3rd 30: 1.9/1.2

1st 50: 1.8/1.1

2nd 50: 1.9/1.1

3rd 50: 1.8/1.1

1st 70: 3.7/0.8

2nd 70: 2.4/1.1

3rd 70: 4/0.8

Part 2

1st attempt

2nd attempt

Crisann and I favoured our 2nd attempt more as it was done more systematically.

From afar, the victim was shot in his leg, explaining the high-velocity blood splatter (in blue). With the shot, the murderer had probably intended to incapacitate the victim so that he could have his way with him. This revealed the cruel nature of the murderer as he wanted to make his victim suffer immeasurable pain before he died. When he was shot, the victim probably fell to his knees and the murderer took the opportunity to ram the back of his skull into the wall once, causing a flow pattern of blood (green at the top left-hand corner of the paper). Medium velocity impact splatters were also evident, indicating that he had probably been beaten. A fingernail probably caused the long contact bloodstain (swipe pattern that runs from the right of the image to the bottom). The thick transfer bloodstain that ran through the flow pattern of blood was probably caused by a blunt object.

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