A former police officer has told a Sydney court he did not have an agenda to prove that former teacher Chris Dawson killed his first wife, Lynette.
Mr Dawson, 73, is accused of murdering Ms Dawson in 1982 so he could have a relationship with the family's 16-year-old babysitter, who was a student at Cromer High School where he taught physical education.
The former Newtown Jets rugby league player has pleaded not guilty and alleges Ms Dawson left voluntarily.
There have been no verified sightings of her since.
John Pendergast, a former detective sergeant who started investigating the disappearance of Lynette Dawson in the 1990s, was on Wednesday cross-examined by Mr Dawson's barrister, Pauline David, about the evidence he documented during his work on the case.
Ms David put it to the witness that he deliberately discarded evidence from people he interviewed about possible sightings of Lynette Dawson after she went missing.
Ms David: "You dismissed things that would mean Chris Dawson was innocent because your theory was that he killed his wife."
Mr Pendergast replied: "No, that's not true."
He denied that he was pushing an agenda and denied that he lost his objectivity working on the case.
Ms David: "You were not impartial at all."
Mr Pendergast: "Yes I was."
Ms David: "You dismissed sightings."
Mr Pendergast: "That's not true."
Earlier, Justice Ian Harrison, who is presiding over the trial without a jury, ruled out calling new evidence.
Prosecutor Craig Everson told the court that up to five new witnesses have come forward, including one who had phoned Crime Stoppers.
Mr Everson said police were still taking a statement from the Crime Stoppers caller, but at this stage, it seemed the evidence from the new witnesses was not crucial to the case.
The court heard some of the new evidence related to things witnesses noticed in 1969, which was the year before Chris Dawson married Ms Dawson.
In disallowing the new evidence, Justice Harrison said a "line has to be drawn", given how late it had emerged during the proceedings.
"My inclination is to not permit the Crown to call this evidence," he said.
The trial continues on Thursday with Crown witness Robert Silkman to give evidence.
The Crown case is that Mr Silkman and Mr Dawson played rugby league together and that on the way home from a Newtown Jets trip to the Gold Coast in 1975, Mr Dawson asked Mr Silkman if he knew someone who could help get rid of his wife.
