When police discovered Lyle and Marie McCanns' missing SUV in July 2010, they found a number of blood-stained items inside.

The outside of Lyle McCann's ball cap was covered with dozens of tiny spatter stains. Later testing revealed it was the elderly man's blood.

Marie McCann's diluted blood was found on a number of food cans that were on the driver's side floor of the couple's Hyundai Tuscon. It's believed the cans were somewhere else when they were spattered with blood.

On Monday, an RCMP blood-pattern expert testified at the Travis Vader first-degree murder trial about what could have caused those stains.

Sgt. Adrian Butler concluded the stains on the hat "are consistent with force applied to a source of liquid blood, matched to Lyle McCann, dispersing blood droplets into the air and onto the hat."

In other words, Butler believed Lyle McCann was the victim of some sort of external force that caused him to bleed. He couldn't say if McCann was wearing the hat when he was subjected to force. Butler was also unable to conclude where the hat was when droplets of blood fell on it.

No blood inside the cap

The bill of the cap was damaged by a bullet hole, but there was no blood found on the inside of the hat.

Defence lawyer Brian Beresh asked, "If someone was wearing that cap and they were shot (in the head), the most obvious thing we'd expect to see is blood on the interior of the cap, right?"

Butler answered, "Not necessarily."  

"You can have a bullet wound to your head with very little bleeding," he said. "If it was a small calibre, they tend to bounce around in a person's head."

During cross-examination, Butler agreed that a defence theory was possible: the blood spatters could have been caused by someone sneezing or coughing in the direction of the hat.

Beresh posed the same theory for the diluted blood stains on the cans of food. Again, Butler agreed it was possible.

Butler had some theories of his own as to why the blood was diluted. He thought the blood could have been mixed with water, rain or even cerebral fluid, perhaps caused by a gunshot to the head or blunt-force trauma.  

Butler admitted he never included the cerebral fluid theory in his report or any of his notes. He didn't even tell the prosecutor about his theory until Sunday night.  

The defence called the theory, "desperate, not scientific." He pointed out there was no other evidence of head trauma such as hair, bone or brain matter found on the food cans.  

Beresh asked the RCMP expert, "Did you do any research on this?"

"Not particularly," Butler replied.  

The defence is expected to call its own blood-spatter expert later in the trial, after the Crown wraps up its case.  

janice.johnston@cbc.ca

@cbcjanjohnston

Report Typo

| Send Feedback