The Little Blue Reasoning Book - Brandon Royal [19]
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Problem 9: Interrogation
Police who are trained in criminal interrogation techniques use questions to obtain information and evidence about the guilt or innocence of the subject being interrogated. There are four possible outcomes: (1) a person did commit a crime and is telling the truth (confessing to a crime they really did do); (2) a person did commit a crime and is not telling the truth (claiming to be innocent when they really did do it); (3) a person did not commit a crime and is telling the truth (claiming to be rightfully innocent for a crime they didn’t do); and (4) a person did not commit a crime and is not telling the truth (confessing to a crime they actually didn’t do).
Interrogators have past statistics to guide them. In short, police interrogators contend that when someone is accused of a crime and interrogation takes place, there is a 75% chance that a given person did not commit the crime, a 20% chance that a person is not telling the truth, and a 2% chance that a person will confess to a crime they didn’t commit. Based on these statistics, what is the chance that a person actually committed the crime and is telling the truth (confessing to a crime they actually committed)?
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DECISION-EVENT TREES
Tip #13: Decision-event trees are a way to represent graphically the multiple outcomes involved in a decision scenario.
Terms such as felony, infraction, misdemeanor, and tort are potentially very confusing for the layperson. How might a first-year law student put these words into a decision tree to help make sense out of case law? One idea would be to view each term in terms of the severity of punishment that a court/jury could impose on a guilty verdict.
How are the following ten terms connected?
Felonies
Civil Wrongs (private)
Infractions
Torts
Homicide
Treason
Offenses
Crimes (public)
Misdemeanors
Breach of Contract
The decision-event tree per Exhibit 3.4 acts as a flowchart to depict logical relationships among legal terms. Civil wrongs, also known as “private wrongs,” occur between or among individuals. A breach of contract occurs when one party “breaks” a legal agreement. A tort is a general term used to describe acts that result in injury to another person (e.g., assault). Crimes, on the other hand, involve the state (public). Informally speaking, infractions are “minor offenses” (e.g., parking violations), misdemeanors are “minor criminal offenses” (e.g., shoplifting), and felonies are “major criminal offenses,” of which homicide (murder) and treason are considered the most serious offenses.
Understandably, the above paragraph is difficult to read. We need a visual representation to summarize the type of crime and the severity of crime. Refer to Exhibit 3.4.
Exhibit 3.4 – Decision-Event Tree of Legal Offenses
Exhibit 3.5 provides an example of a decision-event tree showing the outcomes associated with tossing a coin three times? There are eight possibilities when a coin is tossed three times: Heads-Heads-Heads (HHH), Heads-Heads-Tails (HHT), Heads-Tails-Heads (HTH), Heads-Tails-Tails (HTT), Tails-Heads-Heads (THH), Tails-Heads-Tails (THT), Tails-Tails-Heads (TTH), and Tails-Tails-Tails (TTT). Even though writing out the possibilities using abbreviated letters is compact, it is not as easy to grasp until supplemented with a visual format. Decision-event trees are notably user-friendly.
Exhibit 3.5 – Decision-Event Tree: Coin Tosses
Exhibit 3.6 – Probability Tree: Coin Tosses
Problem 10: Set Menu
A restaurant offers a set lunch menu. Diners have the choice of choosing between one of two appetizers (soup or salad), one of three main courses (pasta, chicken, or fish), one of two deserts (pie or cake), as well as coffee or tea. Draw a decision tree showing the total number of ways a diner can choose his