**Core Concept**
The core body temperature in a post-mortem scenario is crucial for estimating the time since death, especially in cases of suspected foul play or unusual circumstances. In such situations, the rectal temperature is more reliable than other methods due to its proximity to the core organs and less prone to environmental influences.

**Why the Correct Answer is Right**
In cases of sodomy or anal trauma, the rectal temperature is a more accurate representation of the core body temperature. This is because the rectum is a thermally stable environment, less affected by external factors like ambient temperature, and its proximity to the pelvic organs ensures a more reliable reading. The rectal temperature is often used as a proxy for core body temperature in post-mortem investigations.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because the oral temperature is highly susceptible to external influences, such as environmental temperature and mouth breathing, making it unreliable for post-mortem temperature estimation.

**Option B:**
This option is incorrect because the axillary temperature, although more stable than oral temperature, is still influenced by external factors, such as clothing and environmental temperature, making it less reliable for core body temperature estimation.

**Option C:**
This option is incorrect because the ear temperature, although a good indicator of core body temperature, can be influenced by external factors, such as ambient temperature, and may not accurately reflect the core body temperature in cases of sodomy or anal trauma.

**Clinical Pearl / High-Yield Fact**
In post-mortem investigations, the rectal temperature is often used as a proxy for core body temperature, especially in cases where the oral or axillary temperatures may be unreliable. This is due to the rectum's thermally stable environment and proximity to the core organs.

**Correct Answer: D.