CSI: St.Lawrence Laboratory Exercise Patterns of Bloodstains

CSI: St.Lawrence
Laboratory Exercise

Patterns of Bloodstains

Objectives: determine some of the characteristics of blood splatters.
Background information: Chapter 6 in your textbook.

Graphs as PowerPoint slide – Due noon, Monday, February 16, 2009

Presentation Assignment – Due Tuesday, February 17, 2009
One presentation per team

Written Assignment – Due Thursday, February 19, 2009
One written report per team

The class will be divided into 8 teams. Each team will examine blood splatter patterns on a different surface:
1. floor tile 2. glass plate 3. wood board 4. cloth

Effect of height of blood drop on splash pattern and size

Materials: ruler
sample surfaces plastic transfer pipette

floor tile artificial blood
or glass plate meter stick
or wood board
or cloth

Procedure:

Avoid getting blood on the tables, floor or your clothes.

1. Place the surface your team has been assigned on the floor or a table.

2. Position a dropper containing artificial blood 10 cm above the surface and allow ONE drop of blood to
drop onto the tile/glass/wood/cloth.

Note: wood and cloth absorb liquid; wait until the blood drops have stopped spreading before you take
measurements.

3. Measure the diameter of the drop in millimeters. Describe the shape of the drop. Note if satellite drops
are present.

4. Clean the surface and repeat steps 3 and 4, two more times. (Note: since it is not possible to clean the
pieces of cloth, one piece of cloth will be used for each height; aim drops in different areas to facilitate
measurements of each repetition)

5. Calculate the average diameter of the three blood drops.

6. Clean the surface and repeat the experiment at four different heights: 25 cm, 50 cm, 100 cm, and
200 cm.

7. Plot the results as height vs. average diameter (mm). Height should be on the x-axis of your graph and
the average diameter should be on the y-axis. Once you have entered your data into an Excel
spreadsheet, select the data with the headings. Under the Insert tab, select “scatter with smooth lines
and markers” to create a graph of your data. (see Figure 1 on page 2)

Patterns of Bloodstains 1

Insert tab Scatter with smooth lines

Figure 1. Locating the Insert tab and Scatter plot in Excel

Effect of angle of blood drop on splash pattern and size

Materials: ruler
sample surfaces plastic transfer pipette

floor tile artificial blood
or glass plate protractor
or wood board
or cloth

Procedure:

Avoid getting blood on the tables, floor or your clothes.

1. Use a protractor to position the surface your team has been assigned at a 10 degree angle.

2. Position a dropper containing artificial blood 10 cm above the surface and allow ONE drop of blood to
drop onto the tile/glass/wood/cloth.

3. Measure the width and length of the drop in millimeters.

8. Clean the surface and repeat steps 3 and 4, two more times. (Note: since it is not possible to clean the
pieces of cloth, one piece of cloth will be used for each angle; aim drops in different areas to facilitate
measurements of each repetition)

4. Calculate the average width and the average length of the three blood drops.

5. Clean the surface and repeat the procedure with the surface positioned at a 45° angle and again with the
surface at an 80° angle.

6. Plot the results: angle vs. average width and angle vs average length on the same graph. Angle should be
on the x-axis of your graph and the average width and length should be on the y-axis. Once you have
entered your data into an Excel spreadsheet, select the three columns of data with their headings. Under
the Insert tab, select “scatter with smooth lines and markers” to create a graph of your data. (see
Figure 2 on page 4)

Patterns of Bloodstains 2

Graphs. Due: noon, Monday, February 16, 2009

Teams must forward their graphs as a PowerPoint slide to my email address ([email protected]) by noon,
Monday February 16. To facilitate presentations, I will download all the slides into a single PowerPoint file.
Images not received by the deadline will not be presented using the digital projector.

Transferring a graph from Excel into PowerPoint using office 2007 is straightforward. Copy the graph
in Excel and paste it into a blank slide in PowerPoint.
To transfer a graph from earlier versions of Excel and PowerPoint:

1. While in Excel, select, then copy, the entire chart area.
2. Open PowerPoint, click on an empty slide
3. Select “Paste Special” from the “Edit” menu.
4. Select “Picture (Windows Metafile)”

the graph should appear in the PowerPoint slide as it appeared in Excel.

Presentation Assignment. Due: Tuesday, February 17, 2009
1. Present graphs of your data to the class
2. Interpret your data.
What conclusions can be made about the effect of height on blood splatter for the surface you tested?
What conclusions can be made about the effect of angle on blood splatter for the surface you tested?

Written Assignment. Due: Thursday, February 19, 2009
1. Provide graphs of your data
2. Interpret your data.
What conclusions can be made about the effect of height on blood splatter for the surface you tested?
What conclusions can be made about the effect of angle on blood splatter for the surface you tested?

Sample marking grid for written report Sample marking grid for oral presentation

/2 presentation of results (graphs) /2 presentation of results (graphs)
height vs avg. diameter height vs avg. diameter
angle vs avg. width and avg. length angle vs avg. width and avg. length
(2 plots on one graph) (2 plots on one graph)

/6 conclusions /6 conclusions
/3 effect of height on drop pattern /3 effect of height on drop pattern
presented presented
based on data gathered based on data gathered
/3 effect of angle on drop pattern /3 effect of angle on drop pattern
presented presented
based on data gathered based on data gathered

/2 grammar and style /2 presentation quality
correct use of English visual aids easily viewed by all members of the class
graphs clearly presented and identifiable graphs easy to interpret/complete
loud speaking voice / clear pronunciation
/10 total correct use of English

/10 total

Patterns of Bloodstains 3

Figure 2. Selecting more than one column of data in Excel

A guide to some features of Excel

To calculate the average value
1. type =average( in an empty cell
2. select the cells containing the values you
would like to determine the average
3. a series will appear.(in example, it is E3:G3)
4. close the parentheses
5. press “Enter” key on keyboard

To copy a formula into adjacent cells

1. select cell with formula Figure 3. Calculating average in Excel
2. click and drag bottom right corner of cell

with formula over adjacent cells

3. the formula in the top cell will be pasted into the selected cells below and the average will be automatically

calculated for each row.

To change or remove the chart title chart title
1. select graph
2. click on the title

To add a chart title
1. select graph
2. select Layout tab under Chart Tools
3. select Chart Title

To add a title to the y-axis

1. select graph y-axis title
2. select Layout tab under Chart Tools

3. select Axis Titles (in Labels section)

4. select Primary Vertical Axis Title

5. select Rotated Tile

6. click on Axis Title that appears in the chart

To add a title to the x-axis x-axis title

1. select graph

2. select Layout tab under Chart Tools Figure 4. Sample graph

3. select Axis Titles (in Labels section)

4. select Primary Horizontal Axis Title

5. select Title Below Axis

6. click on Axis Title that appears in the chart

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