Answer:
It is an opinion because it cannot be proven using objective evidence.
Explanation:
Claiming things for other people is always an opinion, because one can never know how other people feel about something.
Especially if one claims, such as the case here, that the crime is still fresh in the minds of every newspaper reader in Iowa. There are lot of newspaper readers in Iowa and amongst them there will surely be some who forgot about that, don't care, didn't read etc.
Their feelings toward this crime are quite subjective, so there is no objective way to prove it. That means that this claim can't be a fact, but rather an opinion of the author.
