Try making sense of this sentence, out of today's free Metro newspaper in the UK:
Having been in Australia for 17 years, a foreign national wishing to work in Australia must be of good character.
You must only be of good character after you have completed your 17 years of residence, but for the first 17 years you get a pass? Or does it mean even after you've been a foreigner in Australia for 17 years you still have to show you're of good character? Does this make any sense even in the crazy world of immigration law? Give up?
The sentence was in fact uttered yesterday by Grant Jones, the brother of Moira Jones, a young woman who was raped and murdered a few yards from her front door in Glasgow last year. Grant is outraged that his sister's brutal murderer, a Slovak immigrant with 13 previous convictions of which four were for violent offenses, was allowed into the UK. It is Grant who has (if I correctly interpret the puzzling sentence above) been in Australia for 17 years. He is mentioning that to establish his authority.
The sentence he uttered is a beautiful example of a dangling participial adjunct.
What he had in his mind, I suspect, was: "Having been in Australia for 17 years, I can tell you from my personal experience of being an immigrant that a foreign national wishing to work in Australia must be of good character." But the underlined part was there only in his mind. For the rest of us out here he had unknowingly set an interpretational conundrum. We can't read his mind. That's what's involved in dangling predicative adjunct cases: a speaker or writer wrongly assuming we will immediately be able to see how to identify a target of predication (in the case at hand, a person who has been in Australia), when in fact we are clueless, at least momentarily while we do a double-take and try to recover.
My claim about these cases, expressed on Language Log Classic here and here, is that they don't really contravene anything in either the syntax or the semantics of English. They're simply thoughtless. This is not about grammar. It's about (usually unintended) discourtesy to the hearer or reader.