broall wrote:
Defendants who can afford expensive private defense lawyers have a lower conviction rate than those who rely on court-appointed public defenders. This explains why criminals who commit lucrative crimes like embezzlement or insider trading are more successful at avoiding conviction than are street criminals.
The explanation offered above would be more persuasive if which one of the following were true?
(A) Many street crimes, such as drug dealing, are extremely lucrative and those committing them can afford expensive private lawyers.
(B) Most prosecutors are not competent to handle cases involving highly technical financial evidence and have more success in prosecuting cases of robbery or simple assault.
(C) The number of criminals convicted of street crimes is far greater than the number of criminals convicted of embezzlement or insider trading.
(D) The percentage of defendants who actually committed the crimes of which they are accused is no greater for publicly defended than for privately defended defendants.
(E) Juries, out of sympathy for the victims of crimes, are much more likely to convict defendants accused of violent crimes than they are to convict defendants accused of “victimless” crimes or crimes against property.
Source: LSAT
In this example the explanation is that it's the expensive private defense attorneys that get these criminals off the hook. The observed phenomenon is the lower conviction rate for people accused of committing lucrative crimes.
This question asks us to strengthen the argument, so we're seeking an answer choice that eliminates a competing explanation.
(A) is irrelevant because it doesn't tell us about why people are not getting convicted.
(B) weakens the argument by providing an alternative explanation. It's not the expensive private defense attorney, but rather the incompetent prosecutor.
(C) is irrelevant. The number of criminals in each category is not important, but rather the conviction rate for each.
(D) strengthens the argument by eliminating a competing explanation - that it's not the defense attorneys but rather that these people actually didn't commit the crime.
(E) is irrelevant. The distinction is between street crimes and lucrative crimes, and not violent vs. nonviolent crimes.