**Core Concept**
In civil negligence cases against a doctor, the principle of burden of proof is applied to determine who has the responsibility to provide evidence and establish the facts of the case. This is a fundamental concept in the law of torts, which deals with civil wrongs and liabilities.

**Why the Correct Answer is Right**
The onus of proof in civil negligence cases lies with the plaintiff, who is the person or entity bringing the lawsuit against the doctor. This means that the plaintiff must provide sufficient evidence to prove that the doctor was negligent and that this negligence caused harm or injury to the plaintiff. The plaintiff must demonstrate that the doctor failed to meet the standard of care expected of a reasonable medical practitioner in the same circumstances. This standard of care is often determined by expert medical testimony.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it shifts the burden of proof to the defendant, which is not the case in civil negligence suits.

**Option B:** This option is incorrect because it implies that the burden of proof is shared equally between the plaintiff and the defendant, which is not the standard in civil negligence cases.

**Option C:** This option is incorrect because it suggests that the onus of proof lies with the court, which is not the case. The court's role is to interpret the evidence presented by the plaintiff and the defendant.

**Clinical Pearl / High-Yield Fact**
In medical negligence cases, the burden of proof can be challenging to establish, and expert medical testimony is often crucial in determining whether a doctor met the standard of care. This highlights the importance of maintaining accurate medical records and seeking expert advice when necessary.

**Correct Answer:** A. The onus of proof in civil negligence cases against a doctor lies with the plaintiff.