One of the Crown's key witnesses was subjected to a gruelling cross-examination at the trial of Dennis Oland on Wednesday. Prosecutors showed the court a brown jacket they say links Oland to the murder of his father, Richard Oland.

Crown witness Sgt. Mark Smith carried a cooler to and from the courthouse Wednesday because the DNA evidence inside needs to be kept in cold storage.

Among the evidence he identified in court, were DNA samples taken from Dennis Oland's brown jacket. Oland was seen wearing that jacket on the day his father was murdered.

Lab analysis showed minute spots of blood found on the jacket that matched the DNA profile of Richard Oland.

Because of the number of samples and exhibits he collected from Day 1 of the investigation, and his role in cataloguing and keeping track of that evidence, Smith spends more time on the witness stand than anyone else testifying at this murder trial.  It's also a role that opens him up to extra scrutiny from the defence.

Lawyer Michael Lacy asked about apparent footprints in the area where the body was found.

“There was, what appears to be, a footwear impression at the crime scene that was not the product of moving the body?"

Smith responded: “Correct.”

If the footprint was not made by police or paramedics while removing the body, the defence suggests it may have been made by the killer.

But the issue was not discovered until a review of crime scene photos three years later.

Lacy exclaimed in court on Wednesday: “You completely missed a footwear impression in the blood. Is that correct?”

The forensics officer replied: “Basically, yes.”

The defence lawyer continued: “You would agree that there were many things you did over the course of the investigation that were not best practices?”

Smith replied: “Yes.”

Smith is expected to be under a vigorous cross-examination for the rest of the week.

With files from CTV Atlantic’s Mike Cameron.