The defence lawyer in the Colton Ferguson first-degree murder trial questioned the reliability of the victim's brother, a key witness in the case, on Thursday.

Ferguson, 21, is accused of killing 23-year-old Heather Rae Thurier at the Stadium LRT station on May 21, 2010.

Travis Thurier was there when his sister was shot by a man with a sawed-off rifle, which was caught on LRT security footage. Thurier testified on Wednesday that Ferguson was the man with the gun.

But under cross-examination by Ferguson's lawyer Ashok Gill, Thurier admitted he suffers from short-term memory loss, which is aggravated by stressful situations such as what he witnessed the night his sister was killed.

Gill pointed out discrepancies between what Thurier told the judge this week and what he said before, both in interviews with police and in evidence given at the preliminary inquiry.  

Thurier testified that the man who killed his sister was carrying a red backpack. But he told police that the backpack was black.

The LRT surveillance video was played in court earlier this week. Travis Thurier agreed when Gill suggested the video "filled in the gaps" in his memory.

Outside court, Thurier's sister Nicole Gladue told CBC News she still has nightmares about the slaying.

"I wake up crying, sweating, and there's a lot of times where I still get dreams where she's coming into where I'm sleeping and hitting me across the head and saying 'Why aren't my kids with you?"" she said. "Yup, it sucks."

Gladue says her family is finding the trial difficult to attend, including her mother who saw the surveillance video for the first time this week.

"We're just looking forward to the end of this, we'll have a peace of mind."  

The trial resumes on Monday and is expected to take another three weeks.

With files from the CBC's James Hees