Student worksheet

1. Watch the following videos with more information on blood splatter analysis.

Video 1.

Blood Stain Analysis | Calculating the Area of Convergence and the Area of Origin (https://www.youtube.com/watch?v=3jFKZaSeNjg)

Video 2.

How to Analyze Blood Splatter Patterns (https://www.youtube.com/watch?v=WgpueIveiFE)

Bloodstain Analysis

Adapted from ASISTM Forensic Investigations: Blood Analysis Experiments.

Experiment 1: The effect of release height on the diameter and shape of bloodstains.

You will be investigating the effect of release height on the diameter and shape of a bloodstain. As a group, read the method, identify your variables and come up with a valid aim and hypothesis for this experiment.

Independent variable (the one you are changing):

Dependent variable/s (the one/s you are measuring):

Controlled variables (the ones you are keeping the same):

Aim:

Hypothesis:

Materials:

Pipette or bottle with eye-dropper – something that will accurately deliver one drop of fluid with a consistent volume.
Stand and clamp – something to attach the pipette or bottle holding the synthetic blood.
Measures: 30cm and 100cm rule.
Synthetic blood
Graph paper
Newspaper
Label sheets like shown below for each height

Trial 1.

Trial 2.

Trial 3.

Height ___________cm

Method:

Decide as a group what heights the droplets will be released from and write these heights into the table provided.
Set up your stand and clamp and sit the stand on a pile of newspaper.
Attach the dropper in the clamp on the stand so it is at the first selected height.
Place the appropriate label under the dropper so the first trial droplet lands under the label Trial 1.
Drop one droplet onto the paper.
Shift the paper so the paper is positioned for the second droplet to land on the paper under the Trial 2 label and then the Trial 3 label. Repeat step 5 for each.
Remove the paper and allow it to dry.
Move the dropper on the stand so it is the second selected height above a second sheet of labelled paper. Repeat steps 5 and 6.
When the sheets with the three trials at each height are dry, measure the diameter of each droplet in millimeters and complete the table.
Graph the average diameter of droplets from each height.

Results:

Table1: ____________________________________________________________________

Diameter of drop (mm)

Target surface material	Trial 1	Trial 2	Trial 3	Average	Drawing of one bloodstain

Graph your results below:

Figure 1: __________________________________________________________________

Experiment 2: Impact surface

You will be investigating what effect the impact surface has on the diameter and shape of bloodstains. As a group, read the method, identify your variables and come up with a valid aim and hypothesis for this experiment.

Independent variable (the one you are changing):

Dependent variable/s (the one/s you are measuring):

Controlled variables (the ones you are keeping the same):

Aim:

Hypothesis:

Materials:

Stand and clamp
Pipette or bottle with eye dropper
Measures: 30cm and 100cm
Synthetic blood (FSB06)
Materials with different surfaces, for example: Cardboard, Plastic bag, Ceramic tile, Carpet square, Paper towel, Wood, Newspaper, Metal, Clothing – socks, jeans, T shirt etc (you will need a large enough sample to be able to do three trials on each)
Graph paper, pencil

Method:

Set up your stand and clamp on top of newspaper.
Attach the dropper to the clamp on the stand so it is 30 centimetres above the bench and so it is at right angles to the target surface.
Arrange the first target surface under the dropper so the droplet lands in the target area.
Drop one droplet onto the surface for trial 1.
Shift the target surface so it is positioned for the second droplet to land in the Trial 2 zone.
Repeat for trial three.
Remove the surface and allow it to dry.
Repeat steps 2-7 with the different target surfaces. When the bloodstains are dry, measure the diameter of each stain in millimetres and fill out the table, including a sketch.
Graph the average result from each different surface.

Results:

Table 1:_________________________________________________________________________

Diameter of drop (mm)

Target surface material	Trial 1	Trial 2	Trial 3	Average	Drawing of one bloodstain

Graph your results below

Figure 1:_____________________________________________________________________

Now answer the discussion and conclusion questions as a group.

Experiment 3 – Direction of travel

You will investigate if you can determine the direction of travel of the blood droplets using two pre-prepared samples. As a group, read the method, identify your variables and come up with a valid aim and hypothesis for this experiment.

Independent variable (the one you are changing):

Independent variable (the one you are changing):

Dependent variable/s (the one/s you are measuring):

Controlled variables (the ones you are keeping the same):

Aim:

Hypothesis:

Sheet A – prepared sheet of bloodstains with information about how the bloodstains were created.
Sheet B – prepared sheet of bloodstains with NO information about how the bloodstains were created.
30cm rule, pencil

Method:

Sheet A

Select a minimum of 4 stains from Sheet A to analyse and carefully observe each stain.
Sketch the shape of each stain in Table 1.
Measure the width and length of each stain and record the measurements in Table 1.
Draw a line down the length or long axis of each stain.
Note any tails, spines or satellites of each stain: they will be found at the front of the stain.
Decide on the direction of each stain.

Sheet B

Select a minimum of 4 stains to analyse from SHEET B and carefully observe a stain.
Sketch the shape of each stain in Table 2.
Measure the width and length of each stain and record the measurements in Table 2.
Draw a line down the length or long axis of each stain.
Note any tails, spines or satellites of each stain: they will be found at the front of the stain.
Decide on the direction of each stain.
Verify your results with your teacher.

Results:

Sheet A

Table 1:________________________________________________________________________

	Sketch the shape	Height @width (mm)	Direction?
Stain 1		H: W:
Stain 2		H: W:
Stain 3		H: W:
Stain 4		H: W:

Results:

Sheet B

Table 1:________________________________________________________________________

	Sketch the shape	Height @width (mm)	Direction?
Stain 1		H: W:
Stain 2		H: W:
Stain 3		H: W:
Stain 4		H: W:

Now answer the discussion and conclusion questions as a group.

Discussion and Conclusion

Answer the questions below in your groups before submitting your work to your teacher.

Discussion:

What effect did your independent variable have on your dependent variable/s? Was any trend observed?
Were there any sources of error in the experiment? What are they? How could these errors affect your results?
Did you note anything else of interest about the bloodstains in your experiment?
What STEM skills are needed by forensic scientists to analyse bloodstains?

Conclusion:

Summarise the results.Was there a relationship between the independent and dependent variable?
Was the hypothesis supported or refuted?
Summarise the evaluation of your experimental procedure, making comments about its success and effectiveness.
Suggest changes in the procedure (or design) and/ or possibilities for further experiments.

Real-life CSI - Bloodstain Analysis

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