**Question:** All are features of an ideal homicidal poison except

A. Rapid onset of action
B. Delayed onset of action
C. No antidote available
D. Limited systemic availability

**Correct Answer:** B. Delayed onset of action

**Core Concept:** An ideal homicidal poison is a substance that causes rapid death, has no antidote available, and has limited systemic availability to avoid detection. Homicidal poisons are often sought after for their ability to cause death quickly and with minimal suspicion.

**Why the Correct Answer is Right:** An ideal homicidal poison should have a rapid onset of action to ensure the victim is found dead before they can alert others or seek medical attention. A delayed onset would give the victim time to intervene or reveal the poison was administered.

**Why Each Wrong Option is Incorrect:**

A. **Rapid onset of action (Option A):** This is a desirable feature for a homicidal poison as it ensures the victim is found dead before they can take action or alert others.

B. **Delayed onset of action (Option B):** As explained above, a delayed onset is not an ideal feature for a homicidal poison since it gives the victim time to intervene or reveal the poison was administered.

C. **No antidote available (Option C):** While this characteristic increases the chances of the poison being attributed to natural causes, it makes treatment more difficult for the victim. An ideal homicidal poison has no antidote available to prevent suspicion when the victim dies.

D. **Limited systemic availability (Option D):** This feature ensures that the poison is not detected by post-mortem examination or forensic investigations. However, the focus of the question is on the poison's onset of action, not its systemic availability.

**Clinical Pearl:** A common example of a poison with a rapid onset of action is cyanide, which binds to the cytochrome c, inhibiting the electron transport chain in mitochondria and causing cellular hypoxia and death.

**Correct Answer Explanation:** Option B (delayed onset of action) is incorrect because it provides the victim with more time to intervene or reveal the poison was administered, making the poison less effective and potentially raising suspicion.