[Grammar] "must be" in reported speech

[Iryn_]

Hello, dear forum users!

He says, "It must be John who took it."
He said that it must've been John who had taken it.

Is the reported sentence correct?
*if not, what should it be?

 

[GoesStation]

The contraction must've is common in spoken English, but you should only use it in quotations in the written language. I wouldn't change the tense of the second verb: write It must have been John who took it.

 

[emsr2d2]

It must have been John who took it.
He said that it must have been John who took it.
He said that it must have been John who had taken it.

All three are grammatically possible. I'm having trouble coming up with a convincing context in which to use the third.