Forensic Scientist
As a forensic scientist, you will work as part of a team to investigate the evidence from a crime scene. Every case you encounter
will be unique and the work may be intense. Communication is especially important because you will need to be clear and
honest about your findings and your conclusions. A suspect's freedom may depend on the conclusions your team draws from
the evidence.
Suppose the most recent case that you are involved in is a hit-and-run accident. A body was found at the side of the road
with skid marks nearby. The police are unsure if the cause of death of the victim was vehicular homicide. Among the case
description, the following information is provided to you.
Accident Report
Date: June 14
Time: 9:30 pm
Climate: 55 degrees Fahrenheit, partly cloudy, dry
Description of crime scene:
Victim was found at the side of a road. Body temperature upon arrival is 84.9 °F. Posted speed limit is 30 mph. Road is concrete.
Conditions are dry. Skid marks near the body are 88 feet in length.
Known formulas and data:
A body will cool at a rate of 2.7 °F per hour until the body temperature matches the temperature of the environment. Average
human body temperature is 98.6 °F.
Impact Speed and Risk of Death
Impact Speed Risk of Death
23 mph 10%
32 mph 25%
42 mph 50%
58 mph 90%
Source: 2011 AAA Foundation for Traffic Safety "Impact Speed and Pedestrian's Risk of Severe Injury or Death"
Braking distance is calculated using the formula $\frac{s}{\sqrt{l}} = k$, where s is the initial speed of the vehicle in mph, l is the length of
the skid marks in feet, and k is a constant that depends on driving conditions. Based on the driving conditions on that road for
the last 12 hours, $k = \sqrt{20}$.
1. Based on the length of the skid marks, how fast was the car traveling before it attempted to stop? Round to the nearest
whole number.
2. Based on the table, what percent of pedestrians die after being hit by a car moving at that speed?
3. Based on the cooling of the body, if the victim died instantly, how long ago did the accident occur? Round to the nearest hour.
4. Can you think of any other factors that should be taken into consideration before determining whether the impact of the car
was the cause of death?
