Ewen Macdonald's defence case has wrapped up surprisingly quickly, with just two defence witnesses called and completing their evidence on Wednesday afternoon.

Macdonald, accused of murdering his brother-in-law, Manawatu farmer Scott Guy, did not take the stand for his own defence in the High Court at Wellington.

He is accused of shooting dead Mr Guy in the driveway of his Aorangi Road home, near Feilding, at 4.43am on July 8, 2010. Police have not found any murder weapon.

The trial is in its fourth week and the Crown called about 100 witnesses in its prosecution case, including evidence from Macdonald's parents and his wife Anna, Mr Guy's sister.

The last of the prosecution witnesses gave evidence on Wednesday afternoon.

Macdonald's lawyer Greg King called just two defence witnesses, which took less than half an afternoon.

Palmerston North electrical engineer Peter Shelton cast doubt on the accuracy of a neighbour's clock - by saying overhead powerlines would not interfere with clocks, the Manawatu Standard reports.

The neighbour earlier said he heard two shots and his clock, which was fast, showed about 5am so it would have been about 4.45am.

Other neighbours have said they heard three loud bangs in quick succession.

Macdonald's other defence witness, US firearms expert Mitchell Maxberry, told the court that with a double-barrelled shotgun it took one second to fire two shots and seven seconds to reload and fire a third.

A shotgun with a seven-round capacity fired three shots in about one second.

In opening the defence case, Mr King reminded the jury Macdonald must be presumed innocent and the Crown was responsible for proving the charge of murder beyond reasonable doubt.

Macdonald was questioned by police for more than 40 hours and always told the truth about what he knew about Mr Guy's murder, Mr King said.

Macdonald had lied to police about his involvement in the theft of deer from a neighbour's property, and an arson and vandalism on Mr Guy's property, but had later admitted his involvement to police.

It was his "eternal shame" he had not told the truth initially, and he would be punished for those crimes, Mr King said.