What Prosecutors fallacy is
The prosecutor’s fallacy is a logical fallacy that occurs when the probability of guilt is overestimated in a criminal trial. The fallacy is named after prosecutors, who are often guilty of committing it by overstating the likelihood that a defendant is guilty. To understand the fallacy, it helps to break it down into several steps.
Step 1: In a criminal trial, the prosecutor must prove that the defendant is guilty beyond a reasonable doubt.
Step 2: In order to do this, the prosecutor must estimate the probability that the defendant is guilty.
Step 3: The prosecutor may overestimate this probability, leading to an overstatement of guilt. This is the prosecutor’s fallacy.
Step 4: The fallacy can lead to an unfair trial, as it can cause jurors to overestimate the likelihood that the defendant is guilty.
Step 5: To avoid committing the prosecutor’s fallacy, prosecutors must be careful to accurately estimate the probability of guilt and not to overstate it.
Examples
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A prosecutor presents evidence that the probability of a suspect’s DNA being found at the crime scene is 1 in 10,000. The jury mistakenly assumes that the probability of the suspect’s guilt is also 1 in 10,000.
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A jury is presented with evidence that the probability of a suspect’s fingerprints being found at the crime scene is 1 in a million. The jury mistakenly assumes that the probability of the suspect’s guilt is also 1 in a million.
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A prosecutor presents evidence that the probability of a suspect’s hair being found at the crime scene is 1 in 100,000. The jury mistakenly assumes that the probability of the suspect’s guilt is also 1 in 100,000.