She would not be a good witness if the case came to trial.
But one good witness isn't the same as a half dozen.
And the killer works in front of two good witnesses.
"She could have turned out to be a good witness."
The guys are good witnesses; the jury believes them and they walk.
They wouldn't make good witnesses for the prosecution or the defense.
He knew, somehow, we had a good witness here, a man who could tell us a lot.
Now all it'd take is one good witness above level six hundred.
He was still shaken but turned out to be a good witness.
She was now under government protection, but not expected to make a good witness.