A question about using proper grammar.

Ok, someone mentioned a news story about these young kids getting caught taking nude pictures of themselves on their cell phones.

Now, there is also a new anti-drug commercial out that insinuates a young girl was high and taken a bunch of nude pics of herself, because she walks outside and everybody is looking at their cell phones and laughing. She calls her friend and explains how high she was, she hopes she didn’t do anything stupid etc…

ok. Now, I made a sarcastic comment directed at this new anti-drug commercial when I saw this news story in this thread.

I typed, “wow, they must of been high.”

A person came into the thread and said, “didn’t you mean, ‘they must HAVE been high?’”.

Which is proper grammar and why? I am pretty sure “must have been” is correct, which is my bad, becauase I typed it in a hurry and without thinking too much of it. But why can’t I say “must of been” too?

You made a spelling mistake. The correct way to preserve your pronunciation is “They must’ve been high.”

I should add, to be perfectly clear, that, as written, the sentence is also grammatically incorrect, but that the grammar error lies in a misapprehension in the spelling of the contracted form of “have.” Therefore, I am more inclined to call it a spelling error (as I would for cases like “there/their/they’re” and “its/it’s.”)

I could’ve had a V8.

Because it just means absolutely nothing and makes no sense. You can say “I am high” and later say “I have been high”, but you can’t say “I of been high”.

Just to clarify the above:

“Must have been” is grammatically correct, but you can also use the contraction “must’ve” . . . which sounds an awful lot like “must of,” which is not correct.

I don’t know, but that commercial is the funniest piece of propaganda since the drowned baby in the bathtub episode of Dragnet.