There are specific ways investigators need to write reports, in order for them to be clear for all of the parties that will need to read them. Each investigative unit will have its own policies, so new investigators will have to have guidance when first writing reports.
Active and passive voice are common problems in writing. Active voice means that the subject is directly before the verb, and the object directly follows the verb.
The suspect robbed the store.
The subject is suspect, and the verb is robbed. The object of the action robbed is store. It is very clear who did what. Who robbed? The suspect. What did the suspect do? Rob. What did the suspect rob? The store.
Passive voice, on the other hand, puts the object first. It is less clear, and the responsibility is last.
The store was robbed by the suspect.
The store was robbed.
The object of the action has moved to the subject slot as The store, replacing The suspect in the subject slot. Passive uses a be verb, like was or is, along with the preposition by or for. In some cases the agent of the action, the suspect, can be omitted and never mentioned. Here, this kind of truncated passive construction just says was robbed. There is no clear agent of responsibility mentioned. This deferment of agent of action or omission of agent of action altogether is why passive voice should not be used and active voice should always be used when making investigative reports, because in reports the agent of the action is always more important than the object of the action.