It's difficult, because it's 100% contextual (Destiny)

by someotherguy, Hertfordshire, England, Friday, May 29, 2015, 13:06 (3260 days ago) @ Kermit

The example I was taught: If I say "I think Kermit stole £10" I'm modifying a factual statement to be an "opinion". But I'm still making a factual statement (Kermit stole £10), just with a qualifier. [That's important. If, without the "I think" the statement is still subjective and can't be measured - e.g. the quality of a produc - it would be different - as it is here]

If I make that statement to a person or people who trust and believe me, and know that I don't joke around, it's very likely that they'll believe that you've stolen my money. And if you haven't I've slandered you.

As you might imagine, it only really comes up in defamation cases, and the technicality exists specifically to prevent people from stating "opinions" to people they know will take it as fact, then hiding behind the words "I think".

Of course, it can be very hard to prove either way without additional evidence because it has to beyond all reasonable doubt.