Passive Voice of the Sentence
The thief was caught by the police.

Explanation
In the active voice sentence "The police caught the thief," the subject "police" performs the action "caught" on the object "thief." In the passive voice sentence "The thief was caught by the police," the object "thief" becomes the subject, and the subject "police" becomes the object of the preposition "by." The verb "caught" is changed to its past participle form "was caught."

Benefits of Using Passive Voice
1. Emphasizes the receiver of the action: In the passive voice sentence, the receiver of the action is emphasized, which is the thief in this case.

2. Makes writing more concise: The passive voice sentence is shorter than the active voice sentence, making it more concise.

3. Avoids blaming: Passive voice can be used to avoid blaming someone directly for an action.

When to Use Passive Voice
1. When the receiver of the action is more important than the performer of the action.

2. When the performer of the action is unknown or unimportant.

3. When the writer wants to avoid assigning blame or responsibility.

When Not to Use Passive Voice
1. When the performer of the action is important or should be emphasized.

2. When the writer wants to be direct and concise.

3. When using passive voice makes the sentence awkward or unclear.

Overall, the passive voice sentence "The thief was caught by the police" is a useful alternative to the active voice sentence "The police caught the thief" in certain situations.