1. Use the passive voice:
a. when we don't know who performed the action or when it is not important to say who performed it.
Example:
• The money was stolen.
• The plane was refueled.
b. when we want to avoid mentioning the agent
Example:
A criminal is sometimes regarded as a hero. (We don't want to say who regards him as a hero.)
c. when we want to focus on the receiver or the result of an action instead of the agent.
Example:
• The thief was caught by the detective.
2. Use the passive with a by phrase:
a. to introduce new information about the agent
Example:
• The money was stolen by a person.
b. to credit someone who did something:
Example:
• The bills were photocopied by FBI
c. when the agent is surprising
Example:
• The money was found by a little boy
You can omit the by phrase in passive sentences if you feel it is unnecessary or undesirable to mention the agent.
Example:
• Why hasn't this crime been solved?
3. Most commonly, the direct object of an active sentence is the subject of the corresponding passive sentence.
Example:
• The police arrested the suspect.
• The suspect was arrested by the police.
However, an indirect object is sometimes the subject of a passive sentence
• The FBI, gave Cooper the money.
• Cooper was given the money by the FBI.
4. We often use modals and modal-like auxiliaries in the passive.
To form the present passive with a modal, use the modal + be + past participle
To form the past passive with a modal, use the modal + have been + past participle.
Example:
The criminal should be arrested.
He could have been arrested before this.
Use have (got) to, had better, had to, must, ought to, and should in passive sentences to express advisability, obligation, and necessity.
Example:
The charges had to be dropped.
Criminal suspects must be charged.
Use can and could to express present and past ability.
Example:
Suspects can't be kept in jail.
The thief could have been caught.
Use will and be going to to talk about future events.
Example:
This prisoner will be tried.
The suspects are going to be released.
Use can't, could, may, and might to talk about future possibility and impossibility.
Example:
The mystery may never be solved.
He can't be released from jail.
5. The passive can also be formed with get. The passive with get is more informal than the passive with be. It is conversational and characteristic of informal writing.
Example:
Will that criminal ever get caught?
Our team got beaten in the soccer game.
Be careful! Although the “be” passive is used both with action and non-action verbs, the get passive is used only with action verbs.
Example:
More research is needed about the causes of crime.
Not More research get needed about the causes of crime.
6. Have or get + object + past participle are used to form the passive causative. There is usually little difference in meaning between the causative with have and with get.
Example:
You should have your car serviced.
I just got my best suit dry-cleaned.
The passive causative is used in the past, present, and future and with modals
Example:
We had the windows washed.
I get my car tuned up twice a year.
She's going to get her hair cut.
7. Use the passive causative to talk about services or activities that people arrange for someone else to do.
Example:
• The detective had the evidence analyzed.
• Sometimes criminals get their hair dyed or shaved.
The passive causative can occur with a by phrase, but this phrase is often omitted. Use the by phrase only when it is necessary to mention the agent.
Example:
• I got my photos developed at the drugstore.
• We had our house inspected by Jim.
Be careful! Don't confuse the simple past causative with the past perfect.
Example:
• They had the grass cut. (simple past causative—someone else cut the grass)
• They had cut the grass, (past perfect—they had done this before a specific time in the past)
Be careful! Don't confuse the passive causative with the expression to get something done meaning to finish something.
Example:
• I got the work done by a mechanic. (passive causative)
• I got the work done by noon. (I finished the work by 12 p.m.)