If a so called witness picks you out in a lineup in a murder case but the statement the witness makes are not facts to the case can he be a good witness?

Answer 1

What matters is that the witness identified you. You are not expected to agree with their statements as to the facts of the case. The only thing important is that the prosecutor believes his testimony is credible.

Additional Answer:

The only important thing is whether finder of fact (the jury or judge in a bench trial) believes the witness, since they, not the prosecutor, will determine if the witness is credible and truthful. If the witness has lied or is even mistaken as to some parts of his testimony, his credibility as to all matters he testifies to can be called into question even the identification.

There is a legal maxim that states "Falsus in unum, falsus in omnibus." This is Latin for "False in one thing, false in everything." If a witness gives deliberately false testimony as to one aspect of his testimony, the jury should disregard any other part of his testimony especially if it is unsupported by other evidence in the trial. Today, this same principle is applied to discredit a witness's testimony even if there is no deliberate lie. Even if the testimony is simply mistaken, it calls into question all of the witness's testimony. The jury would be free to disbelieve any or all of that witness's testimony as it sees fit in the proper execution of its function.

Added: At the stage of the process, clearly referred to in the question, the ONLY important thing is that the prosecutor believes the witness to be credible, and therefore usable as a witness.

Lets not jump ahead to the trial before we've even gotten past the line-up identification. At that stage of the process the defendant hasn't even been charged yet.

No prosecutor is going to put a witness on the stand and risk their case, if they don't believe the witness' testimony or identification to be credible.

AFTER the case goes to trial the second contributors scenario can come into play, and the judge/jury will get their chance to evaluate the testimony given from the stand.