## Core Concept
Puppe's rule is related to forensic medicine, specifically dealing with the estimation of the post-mortem interval (PMI), which is the time elapsed since death. This concept is crucial in investigations to reconstruct the timeline of events.

## Why the Correct Answer is Right
Puppe's rule is utilized in the context of rigor mortis, a well-known post-mortem change. Rigor mortis is the temporary stiffening of muscles after death, which can be used to estimate the post-mortem interval. According to Puppe's rule, if rigor mortis is present in the smaller muscles of the body (like those in the face or the hands), it indicates that the process has begun and can help in estimating how long it has been since death occurred.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because Puppe's rule specifically relates to the distribution and onset of rigor mortis, not to other post-mortem changes like livor mortis or algor mortis directly.
- **Option B:** This option is incorrect as Puppe's rule does not primarily deal with the process of putrefaction, which is a later post-mortem change involving the breakdown of tissues by bacteria and enzymes.
- **Option C:** This option might seem plausible but is incorrect because while temperature changes are crucial in estimating the post-mortem interval, Puppe's rule specifically pertains to the muscular stiffness associated with rigor mortis.

## Clinical Pearl / High-Yield Fact
A key point to remember is that Puppe's rule helps in estimating the post-mortem interval by assessing the spread of rigor mortis. For instance, if rigor mortis is present in larger muscles like the elbow or knee, it suggests a longer period has passed since death compared to when it's only present in smaller muscles.

## Correct Answer: D.