The rhetorical term for this sort of thing is hypallage, or transferred epithet, and usually it works fine (as in 'he had a sharp tongue'). But this time it doesn't. The police meaning of 'suspicious' can be used about people too. So what are we to conclude when we hear of 'a suspicious person'? That there is something fishy about them, or merely that they are the mistrustful type? Could be either.
The ancient Romans, from whom English took the word, were even more ambivalent about it, since suspicere also meant 'to admire'. But the Romans, with their smaller range of words, had more excuse. Such confusion should never have been necessary, because there was a good alternative in another word from Latin - 'suspect'. It is already used as a noun by police about those they want to question. If we were logical, we would reserve 'suspicious' for people's feelings and 'suspect' for the cause of them.
But we aren't, so we don't, and now we never will, because 'suspect' has gone its own way. It can be used of the smaller irritations, such as milk that might be sour, or a possibly defective machine. It lacks the sense of deep unease we get when we hear of a man dying 'in suspicious circumstances'.Reuse content