How have the courts treated the testimony of defendant's witness in a civil case?

So far as the jury was concerned, it not having heard the discussions in chambers concerning Salvadore, he was a defendant's witness, even though it appeared that he had been subpoenaed by plaintiff. When, testifying for the first time under oath, he denied talking to the officer, other than giving his name, undoubtedly all the participants in the case were surprised. (The judge apparently was, for he then called the witness' attention to the fact that he was under oath.) It then became necessary in fairness for defendant to impeach him. '[T]here are cases that permit impeachment not because the trial testimony was detrimental, but because of the psychological loss of position before a jury caused by a disappointing witness,.' (People v. Spinosa (1953), 115 Cal.App.2d 659, 667, 252 P.2d 409, 414.)