Justice?

Partially you are right. Myrl Redding´s death by hanging was unjust, but you´ve also got to see it this way:

Myrl was not put to death for his false testimony. He was put to death, because of the letter he wanted to send to Billy, where he announced that he was planning to break the conditions for the amnesty offered by the Governor.
In the eyes of the jury that meant that he accepted the death of the rancher´s wife in the name of Justice, which made him guilty of murder in the eyes of the jury.

I personally do not believe he ever realized that the Rancher´s wife died because of him until it was discussed in the courtroom, since he was obsessed with making Ballard pay for what he had done to him and never saw her dead, since the Rancher drove him away with bullets motivated by an unreasonable fear caused by Redding´s violent actions.

Therefore, in short terms, Redding paid for a murder he did not commit, but the jury´s decision to declare him guilty of murder, forcing the judge to condemn him to death because of it, is understandable and Myrl realized that, too.
It makes Redding´s fate especially tragic and Judge Tolliver fully realized that. This realization caused Judge Tolliver to subsequently develope deep anger against everyone that did wrong to Myrl Redding, creating justice on the way.

Myrl was in a no win situation at the end, reminding me of the Richard Gere movie "Sommersby"!!!

Just Watched the movie,It was great until the ending!Justice,politics and money go hand in hand!