BATTLEFORD, Sask. -- Saskatchewan's Court of Queen’s Bench chief justice addressed some inconsistencies Friday in the testimonies from Crown witnesses at Gerald Stanley’s second-degree murder trial.

Stanley, 56, is accused in the fatal August 2016 shooting of 22-year-old Colten Boushie.

Justice Martel Popescul's mid-trial instructions to the jury, on day four of evidence Friday, came after a day in which some Crown witnesses — one who said he was with Boushie when they drove onto the Stanley farm and another who said she saw the killing — admitted on the stand that they made changes to their stories and lied to investigators.

"Common sense tells you that if a witness says one thing in the witness box, but has said something quite different on an earlier occasion, this may reduce the value of his or her evidence," Popescul told jurors Friday before the Crown rested its case.

Court has heard Boushie was sitting in the passenger seat of a grey Ford Escape SUV when he was shot to death on Stanley's farm. Boushie's friends have testified that they were looking for help with a flat tire when they went to the farm.

Stanley's son has testified that his father told him he was only trying to scare the young people away and the gun just went off.

Popescul was addressing the testimony of Eric Meechance, Cassidy Cross and Belinda Jackson, who were in the SUV with Boushie.

Cross admitted Thursday that he had lied to police in his initial statement about carrying a gun, how much alcohol he had consumed and about breaking into a truck on the day his friend was killed.

Jackson initially told police she saw a woman on the property holding a gun.

"I wouldn't say I lied to them. I didn't tell them the whole truth," Jackson said Thursday. "Everything started coming back to me later when I was on my own."

Popescul said jurors should consider any explanation the witnesses gave for the differences.

"Consider whether the differences are significant," he said. "You should also consider the fact, nature and extent of any differences when you decide whether to rely on their testimony."

An autopsy report filed as evidence said Boushie had a blood-alcohol level more than three times the legal limit when he was fatally shot. In Canada, legal intoxication is 80 milligrams.

Forensic pathologist Dr. Shaun Ladham detailed in his report that Boushie was a reasonably healthy young man. He said there were no other significant signs of trauma other than a bullet wound that entered just below the left ear and exited through the right side of his neck.

Ladham noted the bullet had a downward trajectory.

Stanley's lawyer, Scott Spencer, told court he planned to present his opening arguments on Monday, but went ahead and called a gun and ammunition expert as the first witness for the defence.

Angelina Irinici is in court covering the trial.