Self-study
In criminal proceedings, defense attorneys occasionally attempt to establish that a suspect was not present at the commission of a crime by comparing the suspect's DNA to the DNA of blood or hair samples taken from the scene of the crime. ████████ █████ ████████ ███ ██ ███████ ███ █████ █████ ████ ██ ███████████ █████ ███ ███████ █████ ████ ████████ ████████████ ██████ ██ ██ █ ███████ ██ █████████ █ ███████ ██████ ███████ ████ ████████ ███ ███ ███ █████ ███ ███ ███████ █████ ████ ███ █████ ██ ███ ██████
Summarize Argument
The author concludes that it would be wrong to let off a suspect just because their DNA sample doesn’t match the sample from the crime scene. This is because DNA tests often mistakenly show two different people as having matching DNA.
Identify and Describe Flaw
This argument draws the wrong conclusion from the given evidence. If DNA tests often fail to distinguish between individuals, that would lead to false positives (mistaken convictions) rather than false negatives (mistaken exonerations).
Exoneration occurs when a suspect’s DNA sample does not match the sample from the crime scene. However, according to the evidence given, the test results may be questionable when samples do match. So the test’s unreliability makes mistaken convictions more likely—not mistaken exonerations.
24.
Which one of the following ██ ██ █████ ██ ███ █████████ ██████
a
It assumes without ███████ ████ ███ ███ ██ ████████ ████████ ██ ███████████ ████████ ██ █████ █████████
The argument doesn’t assume this; it concludes the opposite. It claims that conclusions drawn from DNA samples can often be mistaken.
b
It confuses a ████ ████ ███████████ ██████████ ███ ███████ ██ ██████ ████ ███ ████ ██████ ████ █ ████ ████ ███████████ █████ ██ ██████ ████ █████████ ███████ ███████ ████ ████ ████ █ ██████ ███████
This describes the author's confusion between two different kinds of errors. We know from the premise that DNA tests can fail to distinguish between two individuals. But this would lead to false convictions, not false exonerations. The author mistakenly thinks that the error discussed in DNA tests is failure to identify two samples from the same person as belonging to that same person. This kind of error could lead to false exoneration.
c
It generalizes about ███ ███████████ ██ ███ ███████ ████ ██ ████████ █████ ████████ ██ ███ ██████████ ██ █ █████ ██ ███ █████ ██ ███████ ████ ███████ ██ ████ █ ███ ████ ████████
The argument doesn’t generalize about other methods because only DNA tests are discussed.
d
It relies on ████████████ ████ ███████ ████ ███ ███████ ████ ████ ███ ████ █████ ██ ████ █████ ███████████████ ███████████
The argument does not appeal to any experimental data, and even if it did, there would be no reason to believe that the data wouldn’t also hold in nonexperimental conditions.
e
It fails to ███████████ ████ ████████ ████████ █████ ████ ███ █████ ██ █ █████ ██ ███ ████ ████ ██ ████████ ████ ██████ ██ ████████ ██ ████████ █████ ████████████
The argument does not need to demonstrate that other kinds of evidence shouldn’t be admitted because it only claims that it’s a mistake to use a DNA mismatch to exonerate a suspect.