Some examples:
Police are searching for the suspects who robbed an East Side man Friday night. They have no suspects in the case.
Sometimes the parrots make things easy. If there are no suspects, of course, there are no suspects. But the first sentence would be flawed even without the second. Police are searching for the robbers. Or you could say they're searching for suspects in the case. And even if the phrase "the suspects" made sense -- if the police had actually identified suspects in the case but were still searching for them -- you don't know that the suspects are, in fact, the robbers. To write about "the suspects who robbed" would not only violate my "write what you know" guideline but also put you at risk of a libel judgment.
Surveillance video shows two suspects ransacking the store.
The video shows burglars or thieves. Again, if the police don't know who the burglars/thieves are, there are no suspects. If they think they know, you don't know whether they're right. Some reporters and editors shy away from burglar and thief and other perp-nouns because they think they're being super-duper cautious about libel. This is misguided not only epistemologically but also legally: If you go around saying that "suspects" committed crimes, where does that leave you when the word actually means something, when a name is attached? It leaves you as the reporter or editor who may have libeled the person behind that name, that's where.
The Boston Marathon case is interesting and perhaps counterintuitive. Because the photos and video clips released did not conclusively show a crime being committed, the word suspect actually was appropriate for a change in reference to the unnamed and then named men being sought by police. And even if the videos had definitely shown bombers, it would have been inappropriate to use that word to describe the actual men with actual names whom police identified as being the men depicted. Maybe they aren't the same people. So you'd have to use bombers in describing that hypothetical photographic evidence but suspects in describing the named men suspected of being those bombers. Write what you know.
The suspect was described as a white man in his 50s.
Such a sentence would make sense if the police had a specific person in mind and were instructing people to help them find him. Usually, though, there is no suspect -- the killer or rapist or robber or whatever is being described.
Police are confident all the suspects have been arrested.
The problem with this one is a little more subtle. Again, it's about that definite article. If there are, say, three suspects, the police don't need to speculate about their confidence; they know whether all of them have been arrested. The more likely meaning of such a sentence is that the crime was committed by a previously unknown number of people but the police are pretty sure the three guys they hauled in are the three and only three responsible. Police are confident no [insert perp-noun]s in the case remain at large. Police do not think they will be making any more arrests in the case.
Police are seeking a person of interest.
Person of interest. Possible suspect. I've even heard of police suspecting that somebody's a suspect. While it is important to attribute allegations and avoid putting words in authorities' mouths, there will be times when a news outlet has to go beyond weasel words and tell it like it is. Don't say police described someone as a suspect in a case if they didn't, but it might occasionally be appropriate, when the search for a so-called person of interest is clearly a criminal manhunt, to call a suspect a suspect in a lead paragraph or a headline. It's not a legal term. (Though you may want to run my advice by your lawyers; libel could be a concern.)
The confessed killer is scheduled to appear in court Monday.
If you saw the confession yourself, that's probably fine. If not, beware. Don't believe everything the cops tell you. In cases with possible confessions or seemingly obvious guilt, the news media are in a tough spot. You don't want to look foolish treating James Holmes as a random dude picked up by the police on a hunch, but you also don't want to set a precedent of pre-judging criminal cases. Hence, James Holmes remained a "suspect" long after it was obvious he opened fire in that movie theater.
You can read more about the problem of parrots in my new book, "Yes, I Could Care Less," which comes out June 18.