Was A a career criminal?
Had he killed before?
If so, did C know that he had killed before?
Was C a career criminal?
Had he killed before?
If so, did A know that he had killed before?
Was one of the two killers a superior to the other?
Were they working for the same superior?
Were they rivals?
Was the purpose of the killing of the wino to send a message to someone?
Were they looking for arms with specific attributes (such as a certain length, or missing pinky finger, or with tattoos, or whatever)?
Ok, so A kills a wino and sends the wino’s arm to C, but C wanted one of A’s arms instead.
Did A agree to send C one of his own arms?
Did C expect to get one of A’s arms from someone other than A?
Was C expecting somebody else to have killed A?
Was A trying to fake A’s death so as to get out of something else that C expected A to do, or in order to stay alive when C wanted A to be dead (by convincing C that A was already dead)?
So can we assume all of the following?
A and C have some kind of plan, which has been described, to the best of my understanding, as not a criminal conspiracy that they’re in together.
To fulfill his part of the plan, A was supposed to send one of his arms to C… 
…and send the other arm to a different address.
C subsequently sees A at the train station with both arms, notes that A has obviously deviated from the plan, since he still has both arms, becomes enraged, and kills him.
Is C blackmailing A? (I’m thinking that takes it out of the realm of conspiracy since A would not be a willing participant.)
Is the person/people/entity at the second address knowingly a part of the plan? (an as-yet-unknown-to-us “D” person, if you will)?
Is this other address a medical facility?
A law-enforcement organization?
Was C angry because A still had two arms?
Would it help to know who the other arm went to?
Had C hired a hitman to kill A and the arm was supposed to be a proof of death?
If so did A send the other arm to the hitman for… reasons?
Was there a wager involved?
No.
No.
No.
No.
No.
I think I have to say, “Yes, A was sending a message to C.”
I think I have to say, “Yes; however, it’s not missing pinky, or tattoos.”
Yes, A agreed to send C one of A’s own arms.
No, C did not expect to get one of A’s arms from someone other than A.
No.
No, A was not trying to fake his death.
Yes, A was trying to get out of something that C expected A to do.
No, C did not want A to be dead. Well, not until C saw A at the train station.
YES!
No.
Yes, the person at the other address is part of the plan.
No.
Yes.
I think I just answered that above. The other person is part of the original plan.
No.
No.
While I was a student at DLI, we’d play Diplomacy with our meetings twice a week. During the other nights of the week, we’d do questions like this. (Yes, we were–and some of us still are–a twisted bunch.) It took my group about a week to get this one. So far, y’all are far ahead of us!
So A was expected to remove both of A’s own arms – and then to be in good enough shape to mail one to C and one to somebody else?
Is A a human being (ordinary sense of homo sapiens)?
Under the terms of the original plan, was A supposed to receive something in recompense for his arms?
Did C just want proof that A had had his arms cut off?
Or was it important that C have that specific arm in his possession?
Are fingerprints relevant? DNA? Other biological markers?
Cutting your own arms off is a pretty extreme thing to be expected to do. Could A have been considered a victim of a crime before these events?
Yes.
Yes.
No.
Yes.
Do you mean having the wino’s arm? No. Having A’s arm? Yes.
No. (I don’t think they are because they wouldn’t’ve come into play at the beginning, prior to the wino’s murder.)
No.
Are we talking about A’s original biological arms, or about prosthetics?
Was C threatening A in some way to coerce him into going along with it?
Was the idea behind all this to deprive A of his ability to perform some kind of arm-requiring task?
I’m getting a Titus Andronicus vibe to this. I know this is not that story, Titus only had to cut of one hand and he actually did it.
Did A agree to cut off their own arms to avoid a different punishment? Either themselves or someone else?
Was A expected to cut his own arm off after cutting off his first arm?
Yes, we are talking about A’s original biological arms.
No.
Yes. (I originally put No, but thinking on it, the answer really is Yes. If I ever see the guy that posed this way back then, I’ll let him know he got that bit wrong!)
Yes, A agreed to cut off his own arms, but No, not to avoid a different punishment for himself or anyone else.
Yes. (I’m guessing, and did guess at the time, that the technology is available to manage that given enough motive and time for both the deed and recuperation.)
It’s possible that I’m wandering astray from what this puzzle is all about, but does the plan include some provision for A to answer the inevitable questions about what the hell happened to his arms?
Does the ability to perform a task that A is supposed to be deprived of have something to do with his profession?
To add, was it expected A would survive?
Was there a way for A to survive the blood loss and shock had he self-amputated? Like he’s in a hospital with docs right there?