Film where husband kills wife with injection and makes it look like she fell of her horse but her parents don't believe this they believe he murdered her

Possibly this?
Murder in Texas (1981) (TV) - Plot Summary (http://www.imdb.com/title/tt0082780/plotsummary?ref_=tt_ov_pl)

Possibly this?
Murder in Texas (1981) (TV) - Plot Summary (http://www.imdb.com/title/tt0082780/plotsummary?ref_=tt_ov_pl)


I think I've seen the movie being asked about. I don't believe it has famous actors in it, not recognizable names such as Elliott and Fawcett.

In the movie I'm thinking of, she seems to have died after her horse threw her, from striking her head on a rock(?). Her family, especially her sister (I seem to recall), are suspicious. It turns out that he injected her with something that wouldn't be easily detected. Could it have been an animal tranquilizer from their ranch?

My memories are hazy, but I think that it could be from the Nineties. I might have it in one of my film journals; I've been going through them to find this answer for someone else.