## Core Concept
A hostile witness is a term used in legal proceedings to describe a witness who provides testimony that is unfavorable to the party that called them. This concept is crucial in understanding the dynamics of witness testimony and the legal strategies employed during trials.

## Why the Correct Answer is Right
The correct answer, **D. Gives testimony against the party who called him**, accurately reflects the definition of a hostile witness. This occurs when a witness's testimony contradicts the expected narrative of the party who called them, necessitating the party to request permission from the court to treat the witness as hostile. This allows the party to cross-examine the witness, potentially discrediting their testimony.

## Why Each Wrong Option is Incorrect
- **Option A:** "Gives favorable testimony" is incorrect because a hostile witness does not provide testimony that favors the party who called them.
- **Option B:** "Is not present in the court" is incorrect because a hostile witness must be present in court to give testimony against the party who called them.
- **Option C:** "Is a character witness" is incorrect because being a character witness does not inherently make a witness hostile; the hostility is determined by the witness's testimony in relation to the party who called them.

## Clinical Pearl / High-Yield Fact
In medical malpractice or personal injury cases, a treating physician might become a hostile witness if their testimony undermines the plaintiff's or defendant's case. Understanding the concept of a hostile witness is crucial for legal professionals and medical practitioners to navigate the complexities of legal proceedings effectively.

## Correct Answer: D. Gives testimony against the party who called him.