There will be one less person on the jury, deciding Phillip Polkinghorne's guilt

One juror has been discharged from the murder trial for the Auckland eye surgeon - for personal reasons.

The juror has a commitment on Friday, which the judge says could pressure the jury to come to a verdict within limited time.

Eight women and three men will now rule whether Polkinghorne is guilty of murdering his wife, Pauline Hanna.

The defence says she took her own life.