reported speech

[grd]

Hi,

I`m learning "Reported Speech" and there are some things that i don`t understand very well.I`ve learned that we should make tense changes when we want to tell someone else what we or someone else has said,but i`ve noticed that native speakers don`t always follow these rules.Is it always necessary to make tense changes? For exampe,is it correct to say:

This man on TV said that she was murdered in 1991.
This man on TV said that she had been murdered in 1991.

He said that he enjoyed his trip to London.
He said that he had enjoyed his trip to London.

[Tdol]

We don't awlays change the tenses- if something is still true, we often leave the originals and in colloquial speech people often don't bother.