#20 - Whoever murdered Jansen was undoubtedly in Jansen’s

[Malila Robinson]

Hi AM4747,
The key to answering the question is in the word "or." What the sentence: "...if Samantha was the murderer, she would have avoided leaving behind footprints or fingerprints" means, is that at least one of footprints or fingerprints would have been absent. In this case we are told that fingerprints were found and they weren't Herbert's, yet Herbert and Samantha were in the office. This does not get us to the point of knowing that Samantha murdered Jansen. The "or" in the sentence means that maybe she did leave the fingerprints, but is just as likely that she would have only left footprints, and since we only know about fingerprints it doesn't mean it was her.

Answer C solves that problem by saying that it was either Samantha or Herbert. And since the stimulus already told us it wasn't Herbert it makes it so that the 'maybe' we posed above is erased, and it was definitely Samantha who left the fingerprints.

Hope that helps!
Malila

[cinnamonpeeler]

"If Herbert had committed the murder, the police would have found EITHER his fingerprints OR his footprints at the scene of the crime." I took this to mean Herbert must have left AT LEAST ONE of his fingerprints or his footprints AND POSSIBLY BOTH.

"But if Samantha was the murderer, she would have avoided leaving behind fingerprints or footprints."

Can you explain why we take the second sentence to mean "fingerprints AND footprints?"

If I had read those two sentences normally (without really thinking very critically about their logical or formal structure) I would have took the second sentence to mean "fingerprints AND footprints." But when I solved the question I took "But if Samantha was the murderer, she would have avoided leaving behind fingerprints or footprints" to mean "Samantha would have avoided leaving AT LEAST ONE OF THE TWO and possibly both."

Can I take every "or" statement on the LSAT to mean "at least one of the two, possibly both"? Or do I need the indicator "either/or"?

What the sentence: "...if Samantha was the murderer, she would have avoided leaving behind footprints or fingerprints" means, is that at least one of footprints or fingerprints would have been absent.

I thought the previous PowerScore staff post had said that the conditional means that if S were the murderer, she would have left both her fingerprints AND her footprints?

[Adam Tyson]

With respect to my colleague, I think that the technical reading of "or" about Samantha is a bit strained. In a positive "or" statement, such as "I will have eggs or waffles," the indication is that I will have at least one and could have both. In a negative "or" statement, however, such as "I will not have eggs or waffles," the meaning is "and not" (like the use of neither/nor). I interpret this stimulus as saying that if Samantha were the murderer she would not have left fingerprints AND she would not have left footprints - she would have avoided leaving either.

In any case, however we interpret that statement, the evidence makes clear that Herbert cannot have been the murderer. How do we then pin the deed on Samantha with complete certainty? We eliminate the possibility that it could have been anyone other than one of those two! Once we know it had to be one of them, and that Herbert didn't do it, Samantha is our killer!

[Blondeucus]

The way I approached the question was as if it was a necessary assumption rather than a sufficient assumption I've read through the other replies and I now see that this is in fact a sufficient assumption question.
What I still don't get however is that if The fingerprints found at the scene of the crime were not Samantha's then she wouldn't be the murderer.
Because in the premise it was stated If Samantha was the murderer she would avoid leaving footprints or fingerprints
So E is satisfying this requirement by Samantha not having left the fingerprints and not having left any footprints then she would be the killer? Obviously this is wrong but I cannot wrap my head around why I would appreciate the clarification.
Forget C I get that if Herbert and Samantha were the only people on the office on the day of the murder then the other premises combine together in showing that it wasn't Herbert therefore it must be Samantha through process of elimination.

[Jeff Wren]

Hi Blondeucus,

It looks like you may be getting tripped up on your conditional reasoning regarding the premise:

If Samantha was the murderer, she would have avoided leaving behind footprints or fingerprints.

All this premise is saying is that if Samantha was the murderer, then HER fingerprints/footprints wouldn't be found in Jansen's office. If the fingerprints that were found that were not Samantha's (as Answer E states), that is consistent with Samantha either being the murderer or not being murderer. In other words, the fingerprints could belong to Jansen, the murderer (if it was someone other than Samatha and Herbert), or just someone else who had nothing to do with the murder.

Counterintuitively, the only way to rule out Samantha from being the murderer in this argument is to actually find her fingerprints/footprints in the office, but not finding them doesn't prove anything in terms of her guilt or innocence.