How does one know which kamma-cetana and action is related to which kamma-vipaka being experienced? For instance if I go to a forest and a dog bites me on my leg while there. 

How do I know whether: 

example 1: 

a) the dog biting me is my kamma-vipaka from my intentions and actions from the past or from a past life 

or 

b) the dog biting me is my kamma-vipaka for being in that forest  

?

example 2: 

I do something bad and something bad happens to me 2 days later. 

How do I know whether: 

c) The bad thing happening to me is related to the bad thing I did. 

or

d) The bad thing happening is not related to the bad thing I did.
?
Acintita Sutta: Unconjecturable (AN 4.77):

&quot;There are these four unconjecturables that are not to be conjectured about, that would bring madness &amp; vexation to anyone who conjectured about them. Which four?
&quot;The Buddha-range of the Buddhas[1] is an unconjecturable that is not to be conjectured about, that would bring madness &amp; vexation to anyone who conjectured about it.
&quot;The jhana-range of a person in jhana...[2]
&quot;The [precise working out of the] results of kamma...
&quot;Conjecture about [the origin, etc., of] the world is an unconjecturable that is not to be conjectured about, that would bring madness &amp; vexation to anyone who conjectured about it.
&quot;These are the four unconjecturables that are not to be conjectured about, that would bring madness &amp; vexation to anyone who conjectured about them.&quot;

In other words, I don't think it's possible to know -- or at least, knowing that would be  an unusual/supernatural ability.
I guess it (the law of karma) is useful as a general rule, too complicated to see in detail. It's like, you can usefully predict that a river will flow downhill, without understanding every eddy and wavelet.

If I were to speculate further, my conventional/modern understanding (i.e. not based on Buddhist scriptures) is that you can't say that &quot;the&quot; cause of something is either instant or related to the past -- instead, an event has both kinds of cause, e.g. a &quot;proximate&quot; cause (what happened near or close to, just before, the event?) and some &quot;ulterior&quot; cause -- in fact, maybe several proximate causes and several ulterior causes (furthermore, samsara has &quot;an inconstruable beginning ... not evident&quot;).
It's difficult, I suppose it's a mind-made projection (see also &quot;sunyata&quot;), to identity any one cause. IMO that's the same kind of difficulty (or impossibility) that you experience when you try to find the single thing which &quot;is&quot; a person (is it their name, their reputation, their fingers, their mood, etc.? Maybe none of these, maybe all).
And yet (obviously or conventionally) people are different, they inherit differences, they react differently, train themselves for better or for worse; and they &quot;reap what they sow&quot;, more or less, though the details can be difficult to decypher, they develop habits -- so it wouldn't make sense to say that &quot;karma doesn't exist&quot; (like you wouldn't say that people don't exist).
I'm not even sure whether every event is considered a fruit of karma -- see also What, besides karma, determines the future? -- e.g. in this video I think Ven. Yuttadhammo is explaining that people dying in a Tsunami is an act of nature, which has various scientific causes, e.g. to do with the movement of &quot;atoms&quot; ... and that &quot;karma&quot; (in contrast) explains the role of &quot;the mind&quot; within that, e.g. why some people will be scared, others angry, others calm.