In English law 'deposition' has a special meaning.It's a record of what a witness says on oath during committal proceedings [the hearing before magistrates where the court rules whether the defendant should be committed for trial by jury] which is signed by the witness as a true record.
So we are a bit wary of advising you ! We can only attempt to help and make certain assumptions applying certain basic principles.This may just be helpful, nonetheless.It rather depends what it is that concerns you.
If in the US 'deposition' means no more than any statement in writing made by a witness or potential witness to an accident and taken by police investigating the circumstances, what we would call 'a witness statement' then what the injured party saw is relevant and it would, presumably, be quite normal for the statement to be taken . The taking of it would not mean that the police thought that the injured party was at fault.It would taken only to help in the investigation.
However, it may be that you are asking about a statement made in the form used for a person who is suspected of committing an offence. If so then we really can't help at all as to why or when or under what principle it was taken. It might be normal in that State, it might not.English law and procedure is different.