The Killer’s Trail
The Product Rule
Forensic Science
9/17/15
Drill: What evidence would you collect?
Make a list of items and what you could find on/from
them.
Mock Crime Scene: http://www.masss.gov
Objectives
• SWBAT
• Name many forms of physical evidence.
• Classify evidence as indirect (circumstantial) or
direct.
• Classify evidence as individual or class.
• Examine the death of Marilyn Sheppard.
• Calculate the probability of various events using
the Product Rule.
The Killer’s Trail
• You need:
• The Killer’s Trail WS
• You will watch “The Killer’s Trail” and
answer questions about it. Also, whenever
you hear a new piece of evidence mentioned,
write it down on the back of your question
sheet.
Sam Sheppard Trial Evidence
• What kind of evidence did you write down?
• Testimonial/ Direct
• Physical/ Indirect
• Come up to the board and write types of
physical evidence
• Class or individual? How was it useful?
What good is class evidence?
• The product rule is a formula for
determining how frequently a certain
combination of characteristics occurs in a
population.
• It is usually used for combinations of genetic
traits.
Example
• 70% of people can roll their tongue
• 14% of people think cilantro tastes like soap
• 1 in 12 men is colorblind, 1 in 250 women is
colorblind.
• What is the likelihood of
• A colorblind man who can roll his tongue and
thinks cilantro tastes like soap?
• A non-colorblind woman who can roll her
tongue, and thinks cilantro tastes fine?
Worksheet
• Turn to pg. 3 in your packet – Product Rule
• Note that these are VERY small percentages
• 3.6% = 0.036, not 0.36
• When done, let’s put these on the board.
• Don’t worry about sig figs—round answers to
two digits.
• (I know, Chem folks. It hurts me, too.)
Closure
• Choose an object.
• List the individual and class evidence about
that object.
• Is there any evidence (fingerprints?) that
could be identified? Compared?