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	Forensics Case 10 Dropped at the Scene: Blood spatter analysis

Activity Overview

In this activity, students graph data to find quantitative relationships and create a standard reference curve for comparison with unknown data. They analyze blood spatters and examine r² values for linear, natural logarithm, quadratic, and power curve fit. They find the curve that best fits the data and use it to determine the height from which blood has dropped.

Before the Activity

See the attached PDF file for detailed instructions for this activity

Print pages 88 - 91 and pages 92-95 from the attached PDFs file for the class

Print sample data and student work pages

Set up the calculator for data collection

Activity Downloads:

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During the Activity

Distribute the pages to the class.

Follow the Activity procedures:

Drop a single drop of simulated blood from a pipette onto a white paper from a height of 10 cm

Measure the diameter of the blood spatter (in mm), and note it in the Evidence Record sheet

Repeat the process and record the average diameters

Repeat the activity for different drop heights

Create lists for height and diameter

Graph the drop height against the average spatter diameter

Perform linear, power, logarithmic, and quadratic regressions on the data and record the r² values

Understand that the curve with r² value closest to 1, fits the data the best

Determine the curve of best fit and record its equation in the Evidence Record sheet

Use this equation to estimate the height from which the blood at the crime scene fell

After the Activity

Students analyze the results, answer the case analysis questions on the Evidence Record sheet; and thus identify Jessica Barnes' killer.

Review student results:

As a class, discuss questions that appeared to be more challenging

Re-teach concepts as necessary

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